Cafe Scientific, Southampton, UK, past talks

Latest update of this file 16 November, 2018

Some details on past SWA science cafe talks in 2010 , including transcripts of talks and Q&A
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Some summaries etc of past talks held at the venue, St Denys Community Centre
Some hosts are not alowing remote linking now , so to view a "forbidden" picture you have to right click on the mouse and select "view". Not verbatim, and there will be homonyms, transcription, transliteration, typing and spelling errors and misattributions in the following write-ups, and also untranscribed potential litigious stuff that sometimes emerges. Q&A , grouped under one "Q" or ? terminator tend to be dialogue with / multiple questions from one enquirer. ? for unheard / masked words , ??? for phrases.

Simon Saggers of Solent Uni: Some Current Developments In Robotics In Manufacturing And Associated Teaching Methods Tuesday 18 September 2018 Given recent developments, how might we best train / educate the upcoming generation of engineers who wish to pursue a career in robotic manufacturing systems? I am a senior lecturer in engineering at Solent University, teaching a variety of topic areas within engineering, to undergraduates on our various engineering honours degree programmes. Primarily I teach topic areas relating to electronic engineering, and mathematics, but also some areas relating to mechanical engineering, control engineering, and robotic manufacturing, too. A little background on Industrial Manufacturing Robots Overall structure/type of manufacturing robots. Articulated - the most commonly seen in manufacturing, particularly automotive  Rotary joints, typically less than 10, but in principal could be more. Each joint corresponds to a degree of freedom of movement (or axis), and most common robots of this type tend to have 4 to 6 axes, could be more. Cartesian commonly seen these days in 3D printers, laying down material in a layered structure - 3 prismatic joints providing linear x,y,z, motion control. Cylindrical - Cylindrical working envelope controlled by a combination of rotational and linear prismatic joints. Move up and down, rotate around and usually the end-effector could move in or out. Used in small scale pick and place applications. So like a series of test tubes , where an automated testing process is being carried out. Polar - Similar principle as above, but with a spherical working envelope. Not truly spherical generally , but similar combination of rotation and translation joints. SCARA - Selectively Compliant Arm for Robotic Assembly. Approximately cylindrical working envelope, with parallel joints that provide selected plane compliance. Rotation in one plane of motion plus up and down usually for the end effector. Typically just 2 positions , up and down, requiring accurate layout for the workspace, so it can actually reach everywhere required. Delta - Jointed parallelograms, looking like a spider often grouped together on gantries to perform complex operations on a workbed below. Domed work envelope with precision movements. We are starting to see deviations from these standard categories these days. So the bits inside a robot. Robotic Joints control of that ,tending to be actuators. Usually like Servo Motors or Stepper Motors, in actuality it is usually more complicated implimentations. For a servo-motor setup you set a control signal , essentially telling a joint a particular angle to move to, perhaps 37 degrees from the starting point. Usually that would be a Pulse-Width Modulated signal, denoted by the duty cycle and mark/space ratio . That goes thru a summing junction or comparator into an operational amplifier , driving a motor . Most crucially you'd then have possibly via a gearing system Feedback Transducers (e.g. Tachogenerators, potentiometer, IR, etc.) actually measuring the angle of twist of the joint in question. Then use the comparator to determine the difference between the angle asked for and the present actual angle. The difference then adjusts the output to the motor. A looped self-correcting system designed to bring the output as close to the required angle as is feasibly possible. This can be improved by including PID (proportional integral derrivative) loops into the system. Where the proportional part is doing much like the previous comparator . The integral part integratees the error signal , the area under the curve, and applies additional corrective signal to that smoothing out lumps and bumps. Move to 37 degrees and the output may wobble about a bit before settling on 37. Most of that wobble is removed by the integral and derrivative action. Gives a signal proportional to the rate of change of the signal. Even more complex processes can come in here. Anothe rapproach is stepper motors. Although its an analogue process, with appropriate PID you can get precise control with low errors but fast response time. Ask a joint to move a certain amount , it will move that amount reasonably quickly , with minimal overshoot and minimum wobble , having got there and will contribute ot the overall accuracy of the behaviour. Repeating on all joints , gives a reasonably well controlled robot. Stepper motors are multiple coils inside the motor, you can pulse different coils and move a series of small increments. They can be used open-loop ie no feedback from knowing where a joint has got to. With older robots you can often year a clicking or buzzing as it moves during the engagement of stepper motors. So sending out or sending back signals would be Digital to Analogue converters DACs or the reverse ADCs. Some sort of digital control that is giving a numerical value that represents a point in the range of motion of the joint. Say you have an 8bit binary controller. So numreical values range from 0 to 255 , 8 binary digits. If the range of a joint was 270 degrees , then divide that by 255 equally spaced rotational points in that range of motion. A simple DAC, a series of resistors with values weighted according to the binary scale so starting with value R, the next would be 2xR, then 4xR . So if you use 5V to represent logic 1 and 0V for logic 0. The amount of current throught the resistor would be weighted by that resistor value according to its corredponding binary value . So all the 1s in your binary signal represented by 5V weighted by the weighted R values, fed into a summing amplifier , adding all together. So what starts as a binary signal becomes a varying analogue voltage and drive the motor of the joint. There are now flash converters , using multiple versions of this in parallel and other types as well. That is for sending a signal to a joint. To get a position reading signal back from a joint you will probably start with an analogue source, varying voltage perhaps related to a varying resistance , convert that to binary for the control software to understand. So ADC first , feed that wiht a binary counter counting from say 0 to 255 bits . Each time it counts up, the ADC is converting to a voltage. We compare the voltage we want to convert via a comparator to a successivlely increasing value . When the 2 values are the same , you know you've hit the right binary value. The comparator wil lswitch off that system and you have the corresponding digital value. A simple ADC, more advanced versions these days. Connected to this system of DAC/ADC/actuators /motors/feedback there is some Control Electronics, defining how the whole system fits together . We tend to use block diagram representations for this. How contributory signals are processed, inputs and outputs. A more advanced mathematical version of how the comparator loop system behaves . There ar ea variety of time domain equations , telling us how a quantity is varying in time. eg how a joint moves in time , how a load is affected, a variety of signals are changing with time. They often involve ordinary differential equations and we use Laplace Transforms to convert those ? terms. This allows us to design control electronics to meet mathematical specs . Communications Protocols (e.g. RS485, Industrial Ethernet, MODBUS, CANBUS, ProfiBus) When you ask a robot to move to a particular spot , it doesn't do it perfectly. So want 37 degrees but it won't necessarily arrive exactly at 37 and it will not arrive at that exact same point every time. So arrange a joint to move to a position , go back to its start position , repeat over and over again. There wil lbe a small amout of variation which tends to follow the Gaussian Distribution curve or bell curve, or Normal Distribution. The probability of the joint arriving where we've asked it to be is quite high but its not the whole graph, there are other probabilities around that. Stil la low probability , not 0 not impossible, of it arriving at a point some way away from the desired point. We can calculate this probability and use that figure in a meaningful way to design the workcell. We'd start by calculating a mean average for a joint variation . Perhaps setting up the experiment described before, ask it to repeatedly go to a point/start/point over and over again, each time measuring the deviation, giving a table of deviations, from that we calculated the mean deviation and the SD. Those would go into one of the probability equations , then use such as integral calculus to work out the probabilities corresponding to the curve unde rthe graph. Or more realistically we'd use tables of data . Its all part of the definitition of what we mean by Repeatability Of Robotic Joints. A crucial figure, specially in manufacturing. ie repetitive tasks where one of the most crucial factotrs is, its done the same way each time. Part of the reasoning of replacing a person with a robot in the first place , should get less variation if all is designed and implimented correctly. Getting that figure for 1 joint, gives you an idea of a cumulative figure for all the joints in a robot Repeatability) is defined as 6s Where. s = (Standard Deviation). So if w ewant to arrive at 37 +/-1 degree , we'd hope that at least 99% of the area under the curve would be btween 36 and 38. Also Control Resolution = (CR) = (Joint Range)/((2n)-1) , Where. n = Number Of Control Bits. A measure of the fineness of movement of a joint. Also Accuracy = ((CR)/2)+ 3s, joining together the concepts of repeatability and control resolution. Al lvery well saying move to 0.001 of a degree but how accurately and reliably it will do it. What is the biggest deviation . Also Spatial Resolution = 2* Accuracy = (CR)+ 6s Relatively small figures for repeatability mm or a fraction of mm for a good industrial robot. We need other things to use alongside robots to use them meaningfully. Work Cells, combination of a robot and surrounding peripheral devices or assembly lines ,it will interact with. So things like Peripheral Transducers and Actuators, other ones not just in the robots themselves. You might want the robot to sense other things in its environment and react to them, so additional sensors. Maybe also conveyors or Other peripherals like 3D Printers . Over this whole process is the overall control Software , an operating system , in the past something proprietary, specific to a maker. Now tends to be more generalised. Also available are SDKs, Software Developement Kits a piece of software that sits between the OS and the Applications or programs to get the robot to achieve a particular function. Also an HMI = Human Machine Interface, allowing non-programmers to interact with the robot. Let us know consider a few examples of robotic manufacturing technologies that have been used in the past Perhaps one of first industrial robots used in a manufacturing environment was ‘Unimate’, used by General Motors in 1961 to handle some simple movement of die castings and welding tasks. It was famous at the time as it was so innovative. Invented by George Devol in 1954.,limited functionality but good for systematic tasks. Memory stored on Magnetic Drum, long before hard drives were around. Appeared on ‘The Tonight Show’ with Johnny Carson, waving a conductor's wand to conduct an orchestra and pick up an instrument . Later examples PUMA - Programmable Universal Machine for Assembly. Initial concept design invented by Victor Sheinman while at Stanford University, then developed into the PUMA series in 1977 in conjunction with General Motors. (Model 761, is a later model circa late 1980s). Used up to the 1990s for some applications. Robots of this era tended to incorporate integrated joints, the actuatoors and sensors inside the joint. Some could be linked to and controlled by ‘modern’ PC computer systems. Programming of functions for this generation of robots tended to be joint-space focused, using coordinate maps. To program a robot to go thru a sequence of movements often the coordinates would be in joint-space map. Its like a s[preadsheet, each column , related to 1 joint and each row to 1 position. So if you wanted one pose of the robot , you'd specify yhe angle of each joint . That would correspond to 1 row of the spreadsheet. If you had multiple rows, ie multiple different positions, running through those sequences , the robot would go thru the same sequance. Then ‘Teach Pendants’ become commonplace, hand-held devices you could fine-tune the robots positions. Range of available peripherals and communication protocols increased. Programming languages tended to be bespoke & proprietary, moved to more standardised protocols , that would work with different pcs and otehr technology. An RS485 port on a robot would have been fairly common around then that could communicate generally. PUMA had a particular application software. The Baxter robot Created by Rethink Robotics in 2011. Marks a significant change in the key features and structures of industrial robots. There was much more variation outside of manufacturing. It has much more capability for sensing its environment , than previous models of robot. A series of sonic sensors around the head , to create a sonic field around it , to detect objects entering its proximity. It has cameras on the head and wrists, also IR sensors on the wrists. Ports on the back to connect all sorts of other types of transducers as well. The software has interaction baked-in , it is collaborative, including emphasised by adding faces. Face changes to express basic type human emotions, for a sense of rapport with human workers around. Robots of this era often incorporate some basic AI capacities. (e.g. for Inverse Kinematics Solvers where Ai might be used). Foreward kinematics means you specify a particular position you'd like the robot to move to by specifying the rotation of all the joints. Inverse kinematics you tell it where you'd like it to end up and you let it work out for itself how to get there, for an optimal or most efficient path for the end-effector , for a task. IK can use AI techniques , not Turrin Test stuff but kinetic algorithms or inference systems or fuzzy logic, or neural networks, that can mimic learning-like behaviours, like a living organism can. Extremely useful for solving certain kinds of task. Awareness can be incorporated by simply importing a CAD model , of a 3D printed object say or a drawing of it. That standard STL file can be fed to Baxter and it would understand the geometry. Or it would understand how to avoid it, ie not try and pass through it, but around it. Such awareness has been innovative. Baxter can be programmed to perform movements in Joint Space or a variety of other Phase Spaces (e.g. Momentum Space), how the momentum of the joints ar emoved , or the velocity of all the joints, in applicatins where speed or momentum are crucial, or the applied forces , so much more flexibility. Movements can also be specified in the form of Quaternion operators to specify joint movements. More efficient, requiring less numerical values and avoids ‘Gimble Lock’, where 2 or mor eindependent axes of rotation can get synchronised together in a detrimental manner. or more conventional Rotation Matrices or Roll, Pitch, Yaw, or X,Y,Z providing flexibility in how movements are specified. Robots of this era often are directly integrated with Vision Systems, allowing visual feedback, via cameras, from the robot’s environment, which provides a wealth of possibilities for how the robot may be programmed to ‘recognise’ and interact with objects eg pick it up, from integral vision rather than a separate vision system. From simple ‘edge detection’, to determining key geometric features of objects, and adapting interactions accordingly. A range of other transducers, including IR, and sonic sensors also allow the user to program Baxter (and similar competing technologies) to be more ‘aware’ of their environment. Crucially, with the appropriate software, this combination of integrated vision systems and other transducers, along with the innovative design of the robotic joints themselves, allows for ‘compliant’ operation, making the device (relatively.) safe for inter-operation with humans. Instead of stopping dead which can still cause problems or of course ignoring it and causing even more problems. It can slow down gently and come to rest next to the object. The object could be a table or a human . Prior to Baxter types, robots were often caged-off , because of lack of awareness of what is around them. A huge leap forward for human-robot interaction in industrial environments. Robots like Baxter are hence among the first generation of Industrial Manufacturing Robots than can be described as ‘Cobots’ co-operative of collaborative robots. This allows for a more ethically sound and sustainable approach to incorporating robots into small-to-medium enterprise manufacturing processes. Workers can ‘train’ robots to perform repetitive and tedious tasks, hence elevating the status of human workers in such job roles to a more supervisory capacity, overseeing the robot’s operations for some specific set of tasks. Industry 4.0 . The idea that industry has gone from the industrial revolution as first stage, to assembly plant, to fully automated using robots, now to robots that can co-operate with humans Additional to industry usage, robots of the Baxter era are powerful research tools in a variety of engineering contexts. For motion studies to corroborate results from fluid dynamics or movement of objects etc. This is due to a range of factors, additional to those already alluded to, including. Use of general programming languages, such as Python & C, rather than bespoke/proprietary languages. Baxter uses SDK/ROS (Robot operating System)/Linux/ (open source), can be distributed, without licencing issues, to multiple users per robot, so that those users can develop software in parallel offline, by, for example, using a bootable USB with this environment installed. A range of visual/simulation environments are also available for offline testing (again, open source), and one can also connect to Baxter via standard networking protocols, such as ethernet, allowing remote connection. Otherwise each time you make a new robot , you must create a new OS, all that work and you're just reinventing the wheel. So use an OS that is independent, or at least partially independent of the physical geometry of the robot , so it is platform independent, and can be migrated across different types. ROS is open source and new functionality can be added by anyone, others can make use of that and everyone benefits. Engineers working in this field have more transferable skills as learning on one robot can transfer to others. It all runs on LINUX and you get Libraries of examples. User and manufacturer interaction through development community. Common platform (ROS) becoming widely adopted by many manufacturers as a de-facto standard. Research initiatives such as the ‘Million Object Challenge’, involving collaboration with multiple Universities, particularly in the US and UK. A database of standard day-to-day objects that baxter can be aware of , so all robots can have an inbuilt awareness of a million objects to start with. Example code in Python, provided by Active Robots UK. How easy it is to get started. You can remotely see how a Baxter would respond to a test program, without having a Baxter. So many programs can be run in parallel even if you have only one robot. Again the simulation environmemt is open souce , licence-free. Compliance because not just using servo or stepper motors but series-elastic actuators now . This came out of MIT from Mathew Williamson a founder member of ? Robotics , his knowledge adding to compliant joints. Baxter solving rubik’s cube. https.// A demo of flexible and dextrous task. The cube solving is just standard cube solving algorithm, the impressive factor is it integrating its vision system with its joint movement. There are other robots that can solve a Rubik blindingly fast , but more dedicated robot. Given recent developments, how might we best train/educate the upcoming generation of engineers who wish to pursue a career in robotic manufacturing systems. Modern manufacturing techniques and robotic technologies are dynamic by their very nature, and subject to rapid change and evolution and sometimes revolution. ROS and use of general programming languages benefits manufacturers, users, and engineers working in the industry through transferable skill sets. Problem Based Learning has been shown to be a highly effective method for enabling engineering students to obtain core problem solving skills, in a variety of areas of study, and, crucially, can help them to develop a robust approach to learning that is adaptable to change. This skill set is highly desirable, and transferable. There are many current pedagogic research papers supporting this approach. At Solent University we use a combination of traditional approaches (where appropriate), and also PBL approaches to teaching and learning. In particular, undergraduate engineering honours degree students in their 2nd and 3rd years of study undertake some group projects using our Baxter robotics lab facilities. These projects allow students to grapple with a challenging and realistic problem, involving creating a manufacturing work cell, consisting of a Baxter robot, a 3D printer, and other peripheral devices and assembly stations of their own design. A lot of design and programming goes into this. Involving real-world problems that occur in industry. This work cell must produce sub components, which they must design to meet an overall product specification, that we provide, and the Baxter robot must participate in this process, and must be programmed to sort between multiple sub-components, to identify, and quality check them, and then to assemble them appropriately, and to finally present them as a finished product. Although these projects are group-based, individual roles and responsibilities, with distinct areas of focus, are assigned to each student. Each domain of responsibility includes an opportunity to solve some distinct and significant part of the overall problem, so that there is room for each and every individual student to demonstrate their skills in. problem definition, analysis, problem solving, testing, experimentation, adaptation, programming, , fault-finding, repair, optimisation, and reporting. The project is a summative assessment, it goes to their grade, but prior to commencing the project work, students must first complete a suite of formatively (does not contribute to their grade) assessed laboratory activities, which build their skill set with programming the Baxter robot, and general problem solving in a robotic manufacturing context, and also help them to develop an understanding of the capabilities, principles of operation, and limitations, of the hardware. This all builds upon underpinning applied engineering mathematics and physics capabilities that they have already acquired and demonstrated in their first year studie,exams,assessments. The key point with this process, though, is that, although we provide appropriate support to the students, during the labs, and, in a supervisory capacity during the projects, the actual summatively-assessed project work is all down to each individual student to manage and to work out for themselves, with only minimal and appropriate guidance or support from lecturing staff along the way, which is what all the literature on PBL says. Regular formative feedback, in a manner consistent with the recommendations of current pedagogic research as to how PBL should be carried out in this context. Also, whilst students get quite a traditional set of taught materials on programming in other units of study, and will have learned to be proficient with C/C++/C# prior to undertaking the PBL units in question, they are expected to take some responsibility for their own learning of Python, ROS, and the Baxter SDK, for the PBL units again, with appropriate support from staff. Students are also encouraged to reflect on their own learning process throughout, and given regular formative feedback, in such a way as to encourage them, not just to simply learn python, and a particular associated SDK/OS platform, but, rather to learn how to learn new programming languages/SDKs/OS platforms, by their own self-directed methods, gathering their own supporting resources as they do, and evaluating the suitability of such resources, all within the overarching PBL context. This is something employers regularly tell us, and from our own,as lecturers, industry experience. On the other hand we don't let them flounder on their own. The idea behind this is that no student successfully coming out of these PBL units of study should ever be likely to have any significant difficulty in adapting to future changes in these kinds of technologies, in industry. A desirable skill set for industry indeed. Q&A Outside of manufacturing and robots, I was thinking of future decades and the care industry and shortages of carers. Has anyone been developing a sort of soft robot in the sense of simulating muscles for arm movement . I don't know what its called biologically , if I close my eyes , I can place a finger on my nose because of some sort of muscle sense , built in? Related to that , in the recent Ebola crisis , I saw there was a company intending to use Baxter in that capacity for handling contaminated material. Robotics in medicine has been around for a while now. Robots that can perform surgery. The idea behind that is they would be guided by an imaging system such as MRI. But it would be operating on a patient and be near a high magnetic field , so no metalic parts in the robot. But for care you would need a softer interaction, more humanized. Your not aware of anything like biological muscle , contraction only and always balanced pairs as actuator? I'm coming from manufacturing rather than healthcare context. I'd like to know about such . To get someone out of a bed of a morning , you don't need mm precision, you don't really need cm precision? There are robotic hoists , roboticaly controlled , but a long way from the sort of robot you are outlining. I know in Japan there is a lot of need for an aging population and they are doing something along those lines. With a JCB and 2 hydraulic rams , simulates the human arm quite well. If you were building a robot to do big stuff, the JCB mechanism is perfectly good . Human muscle cells have position sensors built in , so the brain knows where the muscles are, just build something like that in there and part there.? Hydraulic systems have much more punch than electrical systems? Technologies like that exist in the form of exoskeletons, a large area of research. In the manufacturing industry , can you foresee a neural base connection coming in, rather fingers on keyboards? And could that replace programming ? I've dabbled in a bit of AI stuff , but you're describing neural-linkage to biological material. Neural links for very basic or niche tasks do exist. Last week I read of some developement to help people with ADHD , a game , designed to increase their focus for longer periods of time with a trans-cranial neural link . So not probes going into brain tissue, so something along the lines you describe. A few years ago , perhaps Harvard, research to develop an artificial hypocampus. Again to replace damaged brain tissue, not my area , but fascinating to see such collaborative approach. Certainly a trend to make robots more collaborative in the manufacturing environment. It would be the next logical strp but I'd imagine it would raise some ethical and security issues. For the likes of industrial robots like used in Fards of Eastleigh when they were working. Doing very repetitive jobs but I imagine the first task of the day is to go to a reference point X,Y,Z , how often would they have to return to that point .? Again ties in with repeatability and the Gaussian plot. For X,Y,Z systems they would often return to a reference but that is often due to tool wear. A robot with an an end effector of some sort of machine tool , then it will often have to return toa station point. There would be calculations built in relating to expectred tool wear, but it can drift. So they can routinely accommodate change in room temperature and stuff like swarf and dust getting into joints? Yes. But as far as dealing with repeatability issues , its less about checking something against a datum , more about designing the systems the robot has to interact with, to cope with the maximum geometric varaiation that you can in principle get , from variation and repeatability. Say a robot had a repeatability of +/-1mm , which actually would be quite poor by the way. You can envision the end effector has having a little sphere at its tip of 1mm in radius . When designing the systems that robot will interact with , in a workcell, eg a sorting station where its picking up sub-components , if they are in full containers or hoppers , you might make a small flanged area around the rim of each hopper that is 1mm in radius. So the end effector would be pushed into the right area to pick-up regardless. Related to that, but you made no mention, I assunmme is haptic feedback. Can they have haptic sensors to somehow give a fuzzy feel to a contact.? One thing that has emerged around robots like Baxter is a research community around end-effector design. Precisely to introduce things like haptics into the systems. And also to emulate more normal human hand movement, for more dextrous tasks. As well as more way-out end-effectors that are nothing like human hands. At the end you referred to PBL , is that what I would have thought is called heuristic teaching?, learning by doing or learning by error perha[s? In a sense yes, but slightly different. It has to be deployed by people not only with enough academic expertise in the field , but also practical real-world expertise as well . In order to know when to steer students in a particular direction or another. At the end of the day, all things being equal, it would be nice to let them take as liong as they need to but we do have to fit it in the standard academic time scheduling. We do provide some guidance but within that they have to be able to experience for themselves. We want them not just to learn the subject material but also how to learn material. So if the material changes is it is wont to do in this sort of field, they know how to cope with that, rather than floundering. It was developed in hypothetical reasoning in a medical context but has since branched out into other areas including engineering. There is a whole slew of papers on PBL for engineering , what works and what doesn't work including social science aspects. You mentioned collabarative , betweeen what 3 students together on a project? Yes , 3 would be typical. Each would be responsible for a different part of the system but w ewould choose a system whereby everone would have an equal amount , whether programming, problem solving, maths/physics , experimental testing . We wil give quite structured guidelines on what they need to have included in that project. That way we ensure each student has an equal but different opportunity . Equal in terms of what it provides them as a learning experience, but different bits of the overall problem. It also gets them used to working in inter-disciplinary teams, important in an indusstrial context. Is that quite rare in the educational sphere, not just Solent Uni? It is relatively newish , but the slew of papers demonstrate it is not rare. By no means is it the norm , lets say. Conventional learning stil lhas its place but a blend with PBL can be successful. We tend to do some pedagogal research around PBL ourselves, having found it successful in implimentation. W103 + S

Tuesday 16 October 2018 3 speakers from the West Solent Solar Cooperative, the large Solar Photo-Voltaic Power Station at Pennington near Lymington (2.4MW 11KV) : Covering the financial foundations for the project, the construction and then operation of the site. Anthony Woolhouse, chairman of West Solent Solar Co-operative with 2 of the other directors, to share our experinece of doing this , how it happened . The red patch to the south of the UK map of solar irradiance, is where our solar farm is. The coastal patch of our part of the country is one of the best areas in the country to have a solar farm. I think ours produces more than most. The field next to ours has lots of geese on ther e. The biggest problem we had , during the preparation of the project. English Nature read our environmental report that said there was the potential for over-wintering geese ot land on your field. We said , not so, because they land next door because there is a pond there, which is also a filled in gravel pit. We unblocked this impasse by inviting them down to our site . The point of connection to the existing electricity supply. We saw this connection being made, a man on a cherry-picker and clipped on our lines from the farm. This 11KV line was in the field already, which helped a lot. And it had been upgraded , the year before we found the field. Even more helpful as you don't want to have to upgrade a long supply line. An aerial shot of the farm showing the IoW. Its about 12.5 acres , sitting quietly in the landscape . We said to neighbours, it will make no noise an it doesn't. There isa gap in the arrays of panels to accomodate an underlying sewer line. We asked Southern Water if we could build panels over their sewer line and they said , well you can but you'd have to move them pretty quick if we want to work on the sewers. So we left it blank . There is also a straight gap , a sight line to the nearby house. The house owne ris a member of our co-op but he did not want to see uniform rows right across his view, could he have a gap there. How do you find a suitable site. We asked an estate agent in Lymington . He took me to a site but was down-wind of a recycling plant with lots of dust in the air, not good when coating solar panels. There was another field, but not on the market. So standing on this field for the first time, thinking, its flat , its south facing , its not overlooked particularly and no-one knows its here. You can't do these things by yourself , so we formed a board. They're all local people, 2 engineers , a corporate lawyer, a sustainability expert who was sustainability manager for the Olympics and someone who was head of the New Forest transition group. I have planning and small business start up skills. So we had most of the required skills in the board. Its about creating a team that can do these things. The board is essentially the same now after 4 years. The site belonged to a family trust who made money from its previous use as a gravel pit. Then it was filled with inert construction waste. We do have some gas monitoring sites on our field though. They thought we wanted to build houses on the site. It took a while to acquire the site , rather that way than having an external landlord. We went to all the neighbours before submitting a planning application. We met the planner on site , which was useful. We did the planning application ourselves . The planners said we had to improve the graphics as it was a bit Heath Robinson. We were also required to get an ecological survey. In the end , no-one objected to the planning application, nobody. For a renewable enregy project that is remarkable. This was because we did a lot of consultation and many people in the nearest area are now members of the co-op. We ran out tenders to build the site and we chose a company Solar Century one of the most established constructors of solar farms. We needed 2.6 million , and were benefited by the Seed Investment Enterprise Scheme and the Enterprise Investment Scheme which gives tax-relief on investments. The government have now taken that away, from community energy projects. We had open days in Lymington and on the IoW. We said we were a local project and the electricity is used locally. But our back-office is is a company called Energy For All , in Barrow-in-Furness. We were their first solar project , they had previously been doing wind-farms up to then. BBC South was a great supporter of us. They filmed us 3 times, once when just a vision , once when the first solar pannels went up and then the first open day with our members. Solent Radio interveiwed us and BBC Inside Out came over later on. We used all the networks we had , so bee-keepers, quakers, New Forest Transition, FoE , networks that each of us were in. W neded 2.6 million and we raised 2.9 million in 6 weeks and had to give 300,000 back. 55% of our members liv within 30 mils of th sit. W also did a bond which pays 5% for 5 yars and 1/5th capital back in ach of th 5 yars, so one lth final yar of that. We are in a rtrirmnt ara and saying to somone its a long-term projct , a 5yar bond did play play well. All th bond holdrs are in Hants. A Quaker group in Soton wer unable to put panls on their roof so they invested in us instad. Its a commutity projctr and the first thing we did was to plant a hedge , hard work as its not natural soil. We got the whips , plantd with protcting tubes, from the Woodland Trust. We are about to remove all those tubes now. Our hedge was not to hide it, planted it as a wild-life corridor, trying to improve the bio-diverstiy. Our ecological survey said, you could only improve the site, as it had ben a gravel pit. We are working with the Hampshir and IoW Wildlif Trust . We planted wild-flower seeds over the whole site and thy describd that as maritime wild-life, coastal plants. Cathy Cook, I'm an engineer on the board and one of the foundr directors. I'd put solar panels on my own roof at home . We are in th New Forest and so a conservation area and you find its difficult to put solar panels on roofs because of their planning regs. So perhaps a field outside Lyndhurst wher ewe could put a solar array, but not vry likely. Anthony came ot m saying he'd found a field , suitabl for a solar farm. I wantd to proceed as it brings benefits in all sorts of ways. So the tchnical stuff. The existing power line across the field, we were limited . SSE said th network had been reinforced in hte last year , meaning we could have a connection. If th lin had not been upgraded , we would not be able to make any connection at all. They said we could have only 2 MegaWatts maximum output. So we had to keep it below 2MW, this was the first parameter. We had 12.5 acrs and we could gt more than 2MW from that area. We wanted a farm with capability more than this limit. Graphing out power output vertically and time of day on the x-axis. 2 curves, the inside one is for 2MW of pannels so a total maximum of 2MW. The upper curve is for 2.4MW of pannels , although we could physically fit 2.6MW. There is a break-even point between cost and benefit of the extra .2MW. Wintertim ouput and mid summer output. At 2MW , mid summer May, June and July part of th curve is shaved off the top. That is the only penalty for having more than 2MW capability on the whole sit. It benefits us , by the shoulders of the curves, mid winter and the othr months you ar gaining more output. This ends up a big gain, although apparently illogical. Its is these gains for the rest of the year and the rest of each day outside noon-time. Q: How do you spill/expel the excess? Its all to do with the inverters, coming up. We have 255W panels, the peak output midday high summer. 9372 of them. This was the fisrst solar farm that Solar Century did with the panels not in portrait orientation but in landscape. Again big benefits . With portrait , when hte sun is low in the sky , and any kind of shaddow on adjascent pannel , that whole pannel, not just the shaded patch, cannot generate very much at all. So if a bit of shading just at the very bottom of a portrait panel then the whole of that panel is out. Put them in landscape then you've only lost one panel out of 2 , if 2x1 aspect. Its possible to increase by 25% , low sun, by doing that. The inclination, the slope of the pannels for this latitude of the planet is 22 degrees, the best angle for that and optimised the separation between rows to 8m . So some shading in the middle of December and very early morning throughout the year. That is the optimum, beyond theat , you are spreading out the pannels so far , that you are wasting pace where more pannels could be placed and gaining power at other times of the day. The neighbours - one house is quite close to the field. They'd lost the site of the gravel pit and no longer huge lorries dumping construction waste , relieved by top soil and grass seeded. Peace and quiet is an important element of all this. So putting a solar farm there, meant no houses could be built there, no vehicles driven round, no industry on that site for the next 25 years. As long as we keep it quiet and make it green , the owners should be as happy as they could be. As a family they were interested , included a son interested in matters ecological. For the different designs, from the different tenders , some of them had one big central inverter , the kit that turns your DC from the panels to AC for the grid. Or lots of small inverters dotted around the farm. When I was reveiwing the specs , given by the different contractors , I was looking at the air flow the central big single inverter room. It was an enormous flow rate that would make an awful racket from all the fans. Going to the decibel ratings , it was something like 65dB at 30m , any nearby householders would hear this all night long. The board discussed this and a big central inverter was out. And B all your eggs are in 1 basket , if anything goes wrong. So we have 64 inverters , all rated 30KW maximum. Thats the point , though we have 2.4MW of generation, its the inverters that control the output, so never more than 2MW being exported. The inverter controls the conditions that the pannels are operating in. There is a maximum power point , every couple of minutes or so , it switches off for a short interval and it swaps the conditions around. In normal use you want to make as much power as possible and the maximum power point tracker is always looking to get maximum power. But when you are at maximum power and its too much , then the tracker will move off the maximum power point until it reaches the amount of power exportable. It basically desensitises the pannels so the energy is never generated in the first place, so not needing to be then thrown away. So no heating or dumping of power required, its not developed in the first place. All done by software. Q: How does it alter the effectiveness of the pannels? Its down to fundamental physics and the energy gap of semiconductor materials. A photon hits a solar cell, an electron is ejected , and being a semi-conductor it does not go back to where it was. There isan electric field and the electron is pulled away, making the circuit. By changing the voltage, that electron is more likely to return rathjer than go round the circuit. When we had decided on the configuration, SolarCentury did a simulation on software PV6 ? to optimise the separation between the rows , panel inclination , sun angles, hedge height around the field. They came up with an output per year of 2.5GW-hours per year. Enough for about 650 homes . I think the biggest solr farm is 15M in Leicestershire. There are 9372 pannels in all on our farm. A flow chart of how the farm was put together. There is a lot of wiring connecting all the pannels together. If end-to-end then 10 miles of panels, so about 40 miles of string-cable. There are strings of 22 panels and each string is connected toan inverter . As only 22 per string, its like fairy lights and all DC in a single circuit. So if one goes out then 22 go out, you wouldn't want 150 panels to fail in one go , say. Then 6 or 7 strings going to one inverter . Its a gathering process . About 10 of those will lead into a distribution board, a green box with 400V output and very heavy cable. So about 1500 panels worth . There are 7 of those , they go to the step-up transformer to go from 400V to the grid voltage of 11KV. Red cable now instead of black as 11KV , 3-phase. This one is Aluminium, the others were copper, so a lot lighter. It passes thru the substation which is like a safety switch, before it joins the grid. THe mandatory piece of equipment , to feed into the SSE network, about 90,000 GBP. This was the first item on the site and it was so heavy the lorry sunk into the ground . We had the sand and gravel neighbours send along a tractor to hault it out. It was the very wet winter of 2013-2014. If something goes wrong on the grid or on the solar farm, this switch will trip out, requiring someone to come in and reset it. Beside the substation is the metering cabinet , the onsite meter, with also a wireless link to the people who pay us for producing the electricity. The output of the substation is fed via 11KV cable up to the overhead grid line over the field. Q: Can the field flood? No, it can get very squashy , no not a safety issue. The kit is above 3 foot off the ground. Q: Is the wiring above ground? No its all buried , of suitable rating for siting underground. The field was just green grass growing there on top of the inert waste. The first works was pile-driving , to take the framework to mount all the panels on. 1065 piles to be drilled 6 feet into the ground, so as much beneath as above the ground. Done in just 3 days. We wrote to the neighbours saying you may wish to go away at this time, it would be 3 days . A well-oild machine , the crew raising the framework took about 1 week. Fitting the panels took about 10 days. Then the electricians arrived , I don't know how they manipulated the thick cables into place. Then 2 days before start-up SSE came in and connected up , with the grid switched off. About a 2-hour outage in a morning to do that. THen go-live 27 June 2014. Al lthat construction took only 6 weeks. Everyone knew what the routine was and no panic, all worked extrremely well. They finished 3 days before the feed-in tarrif dropped, w ejust made it in time. There is a video on our website , West Solent Solar, and down to construction movie. Our generation is now above budget. Simulation showed us we should have about 2.5GW-hours per year and we're actually making 2.78 on average over the 4 years of running , 11% more than expected. Due to us being in a very sunny spot and because we are right on the coast we always have some wind blowing, what with sea-breezes and a funnel effect from tthe IoW. Even the hottest days thgis summer , you could always feel a breeze. These breezes cool the panels , to counter the heating from the sun. That cooling reduces the resistance and increases the current flow. Tuesday a week ago, our power output , perfect for a full day with only a few dips from whispy cirrus cloud. Even in Autumn we had a peak of 1700 KW. In contrast the Sunday after, extremely wet . It just shows how it would not be worth trying to generate at a very wet site. This Sept we were 20% above budget, only 5 days in the month were low, 25 days of good generation. How about when things are going wrong, how do we know. Also maintainence when things are not quite right. In the early life of the farm , someone noticed we were there and a post-grad student needed a test-bed solar farm for a drone with thermal inmaging camera and would spot hot-spots. Some photos of the drone and its monitor and what we got back later, some images of orange stripes , but a black circle around one spot , a very slight whiteness to the yellow , meaning something hotter than normal. I have a FLIR thermal imaging static camera that is high resolution and we could on the ground to that panel. Immediately we could see what the problem was . A big wody weed had been growing to the south of the panel and it cast a shadow permanently across the panel, producing an area of high resistance a hot-spot . Diagonally opposite that hotspot on that panel was also misbehaving , the reason for that extra spot unknown at this time. There were about 3 other instances of hotspots, those down to bird poo, big splodges. Even if it rains it does not wash off easily. So we make sure we cut the weeds down in front of the panels , about twice a year keeps that under control. We wash all the panels to make sure there is no big build up of detritus. Such a wash once a year is adequte for this. Cleaning with de-mineralised water , doing it about June because the birds are active Aptil/May and June means its hot enough for the panels to dry quickly. So we spotted 4 panels out of 9372 that were faulty, we have some spares about 18 as part of the package of the setup. Unplugged them and replaced them , The old panels wer estill working but not fully . In terms of maintainence we have 25 year warranty on the actual solar panels. On the framework also 25 years, galvanised steel called magizinc . The inverters are a 10year warranty. We had a number of issues in the fisst year where pretty much each inverter had a failure of some sort. The manufacturer could not slide on that and they had to fix them . In the end they did a complete overhaul of all 64 inverters and no major problems since, just an odd minor problem we could sort ourselves. We know if an inverter has gone wrong because we have remote monitoring. A satellite dish and comms to our monitoring centre and they tell us on our pcs at home. We also have an operational maintainence contractor who monitors . There is aproject with Soton Uni who are going to also use a thermal imager on a drone and go down to string-level monitoring. Which would give us an enormous amount of detail. We have enough info as it stands , to make sure we don;t have any major operational glitches. Q: Who made the panels A company called Qcells , originally Germany, moving to Poland and ownership transfering to S Korea , called Hanwai. Q: What would you say was the minimum amount of land for a solar farm? About 0.5MW so 2 to 3 acres. It doesn't have to be on the ground, it could be on a warehouse roof. Many of the big logistics warehouses for supermarkets have panels on their roofs , so are solar farms. Q: Railways have lots of embankments and it occurs to me you could put loads of panels along them? There are 6 test sites being develooped at the moment to supply power to the third rail of Southwest trains. Its DC to DC slthough the first ones will be DC via inverter to AC for a cable alongside the tracks and then inverters back to DC at certain places. One is at the oil depot north of Soton . That railway project is being done with Imperial Colledge. Not only operating the site, but some other activities. I'm heavily involved with school visits, 35 school groups attended, 800 kids over 4 years. You do need a toilet , but the first toilet got blown over in the gales. We put in a lottery grant to put in a composting toilet . Alittle wooden building , all selfcontained. It doesn't smell, doesnt use power or use water , just a hand sanitizer on the wall. A visual aid for the kids, a single panel driving a train set round a track, until you place a kid in the sunpath. An open day for the local dignitories. 2015 was the big tory hit on solar panels and renewable energy . We had BBC south along and with them were 2 people from Cambodia, so they could go back to Cambodia and vreatea solar farm themselves. Biodiversity management. We had Hampshire & IoW wildlife trust come and assist us with the early planning and providing the seed for seeding the whole field after construction was over and they continually monitor its progression. Its a field in recovery, its been dug up , filled with rubbish, covered with grass . We lost 3% of the grass to the solar farm , just 3%. When they dug out the roadway , they produced soil heaps. They were going to spread that soil around the field. When the constructors were there they had doubled up portacabins for themselves , but gave an excellent view over the site. So we got them to move all the soil heaps into one spot for a veiwing platform. So for next to nothing , we got a veiwing platform with a ramp for disabled carriages. An important group of unpaid volunteers were involved transformong the site. Twice a year a flock of sheep are brought onto the site to eat the growth and dropping fertilise the soil as well. Rich patches of flora were the droppings had been. Its been pretty fast generating good growth. These are the mowers twice a year, most of the mowing. We no longer bring in mechanical mowers , just a strimmer to take out tall weeds in the front of the panels. The height of the panels is high enough for a sheep to get under. Q: Do the sheep or other animals interfere with hte cables? Around the inverters we put in sheep fencing so they cant get to the cables. We had a detailed reveiw of where sheep could get to around the site. Also via the Wildlife Trust a Malaise Trap? concerning insects and how they are coming back. When we first came to the field in 2013 it was Springtime , but silent, no insects or birds heard. We didn't know it then but no insects in the soil either. When w edug holes for the trees, no insects. Some insects on the patches of original soil but where the grass seeds had been strewn on the new soil, nothing, very odd. We are now getting good levels of insects back on the solar farm. We have reptile mats around the site and the first snake, a slow worm . We're delighted how its doing. Q: Any issues with being near the sea, from salt encrusting etc.? We do. Everything has been specified as materials to cope with a marine environment, so the extra salinity . The matalwork of the frames is made for a marine environment. Q: Sea breezes covering the glass with salt, or pitting of the glass ? Not a big issue Roger Munford What could happen in the future . When it was built , things have changed even since then. There is a lot of tech around for remotely monitoring and making th grid more efficient. What was National grid switching power stations on and off is now being devolved locally. The distribution netweork operator, SSE for us, they are now doing National Grid type stuff. Handling smallrt assets like solar farms and batteries etc. Small operators like ourselves can be now involved with what was traditionally big-time operators onl;y. Hopefully thos sort of tech will be of more use to the solar farm. People often think batteries will be important , so solar power can be used at night. That will not be the use of batteries though. A graph of generation and consumptin, which has to be equal as there is no storage in between. Whatever is generated is being used. The grid does the magic of balancing the two, Night time consumption in the graph is very low , it goes from 25 to 40GW over about 2 hours in the morning and the grid balance that by switching on a lot of generators. THe red line is fossil fuels, mainly gas, blue line is nuclear and green is renewables and the other line is omport from France and Holland soon to be expanded to include Germany, Iceland and Denmark. The reneawables is a small part of the graph on that particular day. The chance of having surplus renewable is a long way off, so batteries used for storage wouldn't be of use for a long time ahead. The gas usage very closely tracks the overall generation. The grid uses the gas as the main control as they are easy to start and stop. Nuclear its a matter of keeping running all the time and renewables always have a priority as they are C free. The same sort of plot but from the last 5 years.The demand has been going down and been going down for many years. The green is going up and hopefully that will go higher. The gas generation follows the consumption almost precisely, because its used as a control. The electricity market is horrendously complex. The price of electrity is always changing through the day. So 7am and in the evening is when most power is required and is when the prices are highest. At night the prices are very low. The Grid would prefer you to be using electricity at night as its cheapest then. Yhey have all that generation capacity and its not used at night. So gas stations are only switched on for a few hours each day. The grid would like to levelise the graph. This large difference in demand means they have to have enough generation sets for the peaks and all the cables in the distribution network has to be thick as its taking all that power , but only for a few hours a day. If they could levelise the plot, then fewer generator sets required, kept running longer and would not need such thick cables. Brittain seems to be the only country where its not standard to have domestic nighttime/daytinme dual tarrifs. Al lmy continental friends are in the habit of switching on washing machines over noght. But in UK industry dual tarrifs is common. Q: If you manage to flatten that curve , would that mean the price of electricity would come down for customers and the grid? It would be more efficient and should be cheaper, less generators need building and less metal infrastructure. The basis of why the smart grid is coming about. If renewables were not on the scene this exercise would still be coming through. Batteries would still be important if there was no wind or solar power. A perfect day solar output on the farm , showing what happens with the 64 inverters. They individually switch off when they reach their personeal limit. So energy is lost in that is not generated at the peak time. Even though we have a 2MW connection , with 64 inverters at 30KW max each and some efficiency loss in the transformer. We have that connection for 2MW and we only use that max capacity for a couple of hours a day. That connection is one of the farms biggest assets. With such a connection battery would be an obvious extention to operations. Q: Could the grid give you extra capacity to go over 2MW? Yes but would require extra cabling, the extra generation would not cover the additional cabling cost. In our geographical area , to take out all the possible power of 2.6MW , if we filled the whole field with panels , something like 2 million GBP to reinforce just to take 2.6MW. A physical limitation, we cannot put more power up the cables that are already there. We are lucky they had locally expanded some of the grid , not knowing we were coming, but it did allow us to put 2MW on to the grid. With 2million type figures it would have to be in a very central place to benefit lots of people. We could take that surplus power and put it into a battery. But that possibility would be so infrequent that it would probably be too expensive , not realistic. If you overlay prices with our sort of generation , our key generation is when prices are low. Another reason we could use battery is to charge the battery with the power that occurs at midday, then release it at night when the prices are high. That time is when the grid would like you to be releasing it, everything is driven by price. The environmental benefit is quite high from storing the power and delay, allowing the grid to flatten out their curve. Q: Have you done a feasibility study of this? Only roughly but the figures don't really add up , but they probably will do in the near future. What would work is if we buy in electricity at the low price. We can probably predict how much solar power we will produce the next day, buy in power cheap, top up with our solar and then sell it on at the higher price. All very business orientated. With the side benefit of helping the grid with their aim of straight line balancing. If that sort of operation occured we would probably not be running it ourselves but as part of a group. Such relatively small operations such as ours, its starting to become feasible that we could expand to these sorts of projects and be included inthe local grid , assisting the national grid. We will keep our ears to the ground , its something that is likely coming up. The big tesla battery in Oz. Its a bit chating, connected to the oz grid doing a power back-up for a big wind farm. On one occassion a coal-powered power station dropped out over a matter of a second or so. On the oz grid they have coal fired generators on standby and turning, burning energy but not actually doing anything, until required. They should provide power within 6 seconds. But the Tesla battery that is 1000 miles away, detected that the power was off and started injecting power within milliseconds. This stopped the grid frequency from going low. Then the coal fired back up could take over , bringing the frequency back. Tesla were/not? contracted to do this. This is the sort of service that batteries are used for in the UK, stopgap services for a few seconds. The main use as it stands at the moment. Peer to peer trading. We're not one of the big six but some pilot projects are going ahead. To sell tiny amounts of electricity on the market. We'll pretend the co-op are running an eergy market and an individual buying power . Instead of going to 1 supplier like SSE they would have the option of buying from me. I have 16 solar panels on my roof and in the summer quite a lot of surplus, in the winter almost none. But I could have a deal with a friend of mine and say that any surplus he can have for 10p . That would not be enough to supply him but he could have another small supplier and buy their power for 11p . Keep going thru all your friends and organisations that provide small amounts of power. So they have a list of friend-suppliers and prices. Beyond that there would be a large supplier like Ecotricity or SSE as your back-up, as relatively unlimited power from them. This is likely to happen within a few years. So the likes of West Solent power could deliver power directly to its members and organised by someone like say the co-op. The Co-op would process all the data, find the power I was generating , how much my friend was buying off me and go thru the list of participants in the system. Feed-in tariffs are going next march but such a sytem as this would make it more feasible for people to continue installing solar . Most domestic generators use only about 20% of the power they generate. So it would be possible to have viable non-subsidised domestic solar . How much of the grid do you think we use to supply our electricity? How far does it go , how near is the consumption to the generation.? Its about a mile and a half. It goes down the local distribution networks and does not touch the National Grid and do not incur the national grid costs. The SSE network control at Portsmouth for this part of Britain, the Scottish bit is controlled in Scotland . They could show me where our solar farm was and its right on the end the line , geographically at the end of the lane in Pennington and the sea shore is about 1/4 mile from us. Our name appears in small letters on their control board. So we know all the power is going back up , into Lymington. So middle of June, no heating on, people don't want a hot dinner, how far would our power get back into the SSE network , and they said it would probably go all the way back up the west side of Lymington , as its split into 2 halves, and probably get as far as the back of Lymington Hospital. So we could confidently say that most of Pennington was cooking lunch on our solar in June , as cups of tea only in June. Q&A What is the return on investment? We've been paying around about 5% a year since we started. On balancing the grid and trying to smoothe out peaks and troughs. Will balancing with batteries and more renewables , will we reduce our carbon emissions overall? There is a lot of power lost with the gas-turbines stating and stopping . So at least savings there, with the big generators running longer. So good for everyone all round. When is your next open day? Something like 05 July Your site is it dead flat or is it slightly tipped to the south? Seeing it from the IoW it did not look flat, but on site you cannot tell by eye. A slight rise to the north. We had a topographical survey and I think 30ft is the maximum height difference from south to north, more than I'd though by looking at it. We also did some test drilling to see wjhat was under the surface, to see what had been dumped there and it was just construction waste. And no subsidence to disturb the platform registration, it must have been well compacted on delivery. How many years before paying back to the initial funding? About 25 years is the expected lifespan of the farm, probably about 12 years. We don#t know what the technological developements in panels will be . In 20 years they could be astounding output. We have a permanent planning permission, so not limited to 25 years , so we could do that. I'm aware that solar PV panels degrade over time, have you picked up any of that over the 4 years.? Meant to be about 0.4% per year but we've not spotted it yet. You do have an insolation meter so you know how much sunlight is hitting the site? THe pyrometers . The old system was a globe magnifying glass burning a hole or a trace in a piece of card. Now done electronically , a metal plate under a glass dome . The metal 0plate is very thin # , absolutely even thickness and the temp of the plate correlates to the amount of sunshine . I think it was about 2,000 GBP each, we've 2 of them in case 1 was on the blink. I was wondering if that degradation over time could be factored in as part of the 2 and 2.4MW difference.? I think its early days . I think they guaranteed 90% over 10 years , we will see. Do you have any security problems from thieves or vandals? We had vandalism on the composting toilet . It looks like a dog got in burrowing underneath and could not get out, then a human battered there way in to get the dog and caused a lot of damage. Very bizarre, it happened 3 times over a year. 24 hour CCTV monitoring . Loads of gates to get thru , a house right next to it. B43 W105

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