Paul Martin

Feasibility study of a Large Scale Photovoltaic Solar Power Plant in Ireland

By Paul Martin

Abstract

The aim of this project is to look at photovoltaic solar panels and the feasibility of using them for grid connection sized applications. The basics of the technology will be explored along with its capabilities to produce energy. How to design a site will be addressed starting with the size of system desired followed by the appropriate choice of location for such a site. The paper will go on to design a possible site to fit the criteria set out and estimate the possible costs of such a site. Finally it will look at the revenue possibilities of a renewable generator in Ireland and ways in which to improve them.

Introduction

Renewable energy is a topic that is becoming more and more relevant in our everyday lives. It is clear from news reports about oil prices increasing due to a lack of supply, greenhouse gases affecting the ozone and causing climate changes leading to the rise of water levels due to the melting of the polar ice caps, that something must change.

Where renewable energy sources come in is their prospective ability to reduce the world's dependency on fossil fuels such as oil, coal and gas. It is important however to realise that when we talk about these new energy producing ideas if it was possible to stop using fossil fuels and have all energy produced by renewable sources tomorrow it would have been done already. However due to the inherent inefficiencies and drawbacks in the different technologies and the mountain of research still to be done to improve these outputs or mitigate these factors this is simply an unrealistic idea at the moment. But as the saying goes "Rome wasn't built in a day" and if for the moment we can at least lesson are current reliance on fossil fuels then this is a step in the right direction.

Without continued research into these technologies we might never get to a stage where our usage and reliance on fossil fuels can be severely reduced if not eliminated completely but with research and the continued growth of the industry's leading to the new innovation and technological improvements that are occurring all of the time I have no doubt that the goal of a more renewable world will be achieved.

The technologies currently being researched are outlined in the following list:

• Hydroelectricity

• Biomass

• Geothermal

• Wind

• Tidal

• Solar

• Hydrogen

While each has positive and negative aspects to them, they each give the potential of producing energy both on their own and combined with other types of production with little or no emission of harmful gases to the environment. The main thing to be aware of when considering these new technologies is that while the capital costs to implement some of the solutions they propose are large now, and it is easier to just continue on burning fossil fuels, one day we won't have a choice and without renewable energy where will we be?

The type of technology that will be discussed here will be photovoltaic solar panels and the feasibility of implementing solar energy in Ireland in large scale grid applications. While the smaller stand alone sites have increased in popularity over the past few years large scale applications have never really taken off as a viable option thus far. Most applications of solar energy in Ireland have been the utilisation of solar thermal technology for water heating in households across the country and the uptake due to government grants and the prospect of reduced heat bills has been quite good although the inclusion of energy generation has not. While this may seem reasonable in household applications where space for panels is limited and the prospective savings on heat costs might be more attractive then the savings offered by energy generation I wonder why on a large scale there hasn't been much interest in the technology. So to investigate why photovoltaic panels haven't been used the technology itself and how it works will be addressed, then the variations of the types of panels will be investigated to aid in the choice of which would be most preferable for a on-Grid site. Important aspects such as the efficiency involved in energy generation will also be discussed. The next stage is to look at the application of the technology in Ireland and what better way then to actually do it. Therefore as part of this feasibility study and general investigation into large scale applications a site will actually be designed using exact figures were possible and best estimates where not. This will enable a possible cost per watt to be derived for such a site and will also enable the profit calculations that are done to be brought in perspective as far as time taken to pay back capitol costs is concerned. Finally some improvements to the system will be discussed including the consideration of whether the system should be connected to the grid directly or not.

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Photovoltaic Solar Energy

Photovoltaic Solar Technology

The basic idea behind how photovoltaic solar panels function is not that unlike a basic forward biased p-n junction diode. A diode is an electrical component which only allows a flow of current through it when a voltage is applied in the correct direction and above a set threshold voltage. A solar panel differs in that instead of applying a voltage to overcome the threshold, i.e. reduce the depletion region, photons of light energy are absorbed by the panel instead and current is allowed to flow. These photons of light that are absorbed cause electron-hole-pairs to form in the depletion region but once they are formed they begin to drift apart, as this happens the electrons are drawn to the n-type region of the panel structure and the holes are drawn to the p-type region. [Horan, K., Daniels, S., EE403 – Semiconductor Devices] When this occurs an open circuit voltage is created and can be applied to a load, for example battery you want to charge or in this case possible output to the national grid.

Structure of a Solar Panel¹

To give a better understanding of the structure of a panel we can look at the figure below and the description given on each component that makes up a panel:

Diagram of different layers that make up a Solar Panel²

A. Encapsulate: A protective layer that is placed over the cell

B. Front Contacts: Conductive material placed on the top of the n-type region to allow it to collect the electrons being emitted from the solar cells

C. Anti-Reflective coating(ARC): Stops the reflection of light away from the panel to improve the photon absorption levels

D. N-type region: A negatively doped layer of silicon, phosphorous can be used for the doping, that would normally be a lot thinner than the p-type region. This is seen more clearly in the previous image of the solar panel structure. It should be noted that this region is not normally a flat surface but normally would look more like a grating with a lot of peaks and troughs. This gives the surface a greater surface area and can lead to more light being absorbed.

E. P-type region: A positively doped layer of silicon, Boron can be used for the doping, that interacts with the n-type region and allows the formation of a depletion region deep into the p-type region

F. Back Contact: This is another conductive material connected to the bottom of the p-type region and allows the creation of a potential across a load when the top and bottom contacts are connected to it.

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Solar Panel Efficiencies³

Before the different types of solar panels available are looked at an important topic to understand is efficiency of a cell. This is a measure of how well a panel can turn photons of light into an electrical output but due to the structure of the materials though 100% efficiency would be impossible to achieve. If single layer silicon is considered as the material used in a solar cell then we can look at the following properties that highlight why 100% can’t be achieved:

• Bandgap: The band gap of silicon is 1.1eV which means any photons of light with a wavelength greater than 1.1µm, i.e. above the visible range of light, is wasted as there is not enough power to excite an electron hole combination. This leads to roughly 25% of light being wasted lost.

• High energy photons: Photons with energy higher than that needed for electron hole recombination it will simply be wasted, usually released as heat energy. Technically if it is twice the needed energy then a second pair could form from the one photon but this is very rarely the case. This sort of loss can drop the efficiency levels by around 40%

• Reflection: As discussed the need for ARC is there to stop light reflecting away from the panel surface and increase absorption. But these are not perfect and can lead to losses of between 10 and 20%

Therefore considering these losses alone the most efficient you could hope to make a panel would be around 25%. Some of these problems can be reduced by such methods as layering other materials with the silicon to improve the size of its band gap or improve ARC technology but so far no massive improvements have been made.

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Types of Solar Panels

Having looked at the general structure of panels I think it would be a good time to look at the differences that different panels can have. Apart from the physical size of panels one of the main differences is the types of material used. The material that is considered for use here is Silicon but more specifically the different structures it can be produced in. Why I will look at silicon structures is while there are different materials that can be used it is the most readily available material and can lead to the production of quite cheap panels. Examples of the other materials however would be:

• Gallium-Arsenide (GaAs)

• Indium-Phosphide (InP)

• Cadmium-Telluride (CdTe)

• Copper-Indium-Gallium-Selenide (CIGS)

There are three main types of silicon structures used for solar cells:

Amorphous Silicon Cells

This grade of cell is the easiest to produce of the three structures as the doped silicon can be poured onto a material such as glass it does not require a growth process like that involved in the other forms of cell. While they exhibit an efficiency of about 13 % in a lab setting, more than likely would only achieve about half of this in an actual installation, this type of panel has become more and more popular.⁴ This is due to a number of factors, 5 of these are:

1. Manufacture: As the silicon is simply deposited on a material then new plasma based deposition techniques can be utilised to produced them on a large scale both quickly and cheaply

Efficiency comparison of different structured amorphous cells⁸

Although they have become popular for the reasons discussed why they have not taken over the market has to do with the fact that their efficiency still can’t measure up to that of the crystalline cells and also due to their ability to be more flexible their predicted life time is generally only 10 years but it is hard to say for definite.

Polycrystalline Silicon Cells

The next grade of solar cell is the polycrystalline cell. These involve a little more effort and time to produce then the previous type of cell, as they are made up of multiple silicon crystals that have been melted and poured into a cubic mould to form a cube of polysilicon. This cube has then to be sliced into individual cells. It is easy to tell if a solar panel has polycrystalline cells as due to their structure they have a very striking looking surface that makes them look to the eye as if they might be broken.

Polycrystalline Cell⁹

These cells are then processed by the addition of contacts and ARC layers before they are connected together to form modules. While you may wonder why you would bother with process over the amorphous cells is clear when you look at the efficiency that these cells can manage. There is a maximum efficiency capability of around 18%, more than likely 13-15% in a commercial cell, which is nearly twice what is achievable with the amorphous cells. This means is that you can have a solar panel array nearly half the size of an amorphous panel array that will give the same output. This can come in especially handy where space is an issue, e.g. small roof projects. But as with all things these extra processes and higher efficiencies mean that price for the cell will increase

Monocrystalline Silicon Cells

The third and final grade of cell to look at is the monocrystalline cell. This is the most efficient type of the three cells mentioned with achievable levels of around 14-17% with a max of around 24%. How this extra efficiency is achieved is by using a method such as Czochralski Growth to crystallize the polysilicon making one crystalline structure throughout and then slicing it into cells and processing them like before. This crystallization process can take around 8 hours to occur so not only does the slow down the production it also increases the cost of the finished modules. The differences in the two processes can be seen in the following picture:

Production of Crystalline Solar Cells¹⁰

Here we can see the extra processing needed for these wafers and as with before though, by doing the extra work and increasing the efficiency means the module size needed for an application can decrease or more energy can be produced in the same area needed for an amorphous or polysilicon array.

Having talked about the different types of panels I think the following illustration gives a good idea just how much of a difference in size the different cells there can be:

Size Comparison between Cells¹¹

Solar Radiation

Possibly one of the most important and fundamental things needed for the production of solar energy using PV panels is solar radiation as without it there are no photons of light and therefore the potential barrier in the silicon would never be overcome. For solar applications solar radiation is normally measured as solar irradiance which is measured in units of kWh/m². This solar irradiance can then be used to calculate solar insolation and/or Peak Sun Hours (PSH) in areas of the earth. Insolation is a measure of the maximum energy achievable on the surface of the earth per metre squared, generally estimated to be around 1000 W/m2 whereas PSH gives an idea how many hours of good sun occur in a region each day.

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The Positives of Photovoltaic Solar Energy

Having pointing out some of the downsides of PV solar energy such as it doesn’t work at night, there are very low possible efficiencies achieved by panels, reduced output if panel is in shaded areas and solar arrays can be expensive to install. I think it is important to outline the positives of the technology:

Once manufactured a panel will not emit any pollutants into the atmosphere, therefore if a solar array was used to power something currently running on energy produced by the burning of fossil fuels reduces its CO2 emission and eliminates them if it itself doesn’t emit pollutants.

• They can be installed independent of the grid power so in remote locations it could be cheaper to set up a solar array to power something rather than bring high voltage power lines and cables to it.

• They can be integrated into buildings therefore saving on space needed for the array and still producing an output.

• They don’t require anything more than sunlight to produce electricity

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Solar Applications in Ireland

Large scale solar applications such as the ones seen in other countries have never taken off in Ireland. While this may not come as too much of a surprise due to the difference in our climate compared to more a sunny location such as Spain or Arizona in America but that does not mean energy could not be produced and some profit made. If this could be done this would lessen the Irish economies reliance on energy produced by fossil fuels. Currently growing trends in the use of solar energy has been seen, for examples the use of solar thermal panels on house roofs for water heating with some integrating some solar PV technology. Also small stand alone applications are becoming more popular for use on electrical devices such as parking metres where by PV solar panels are mounted on top on the meter which is quite an ingenious way of saving on the power needed for them to run and as the price of the PV panels begins to drop I have no doubt that more and more of these sort of standalone solutions will start popping up on houses, sheds etc.

As mentioned though while the small scale applications are growing and flourishing the large scale applications are yet to take off and what I hope to address is if they would be a worthwhile to set up a plant like that seen abroad here in Ireland. To begin with the predicated output of a solar panel in Ireland needed to be established and to determine this firstly we must look at the source of the power. In the case of solar energy the source is solar radiation but it is not this figure that is used directly but rather the solar irradiance which was mentioned above. There are many websites from which these values can be simply read of maps but unsure of their accuracy I decided to try and see if I could calculate my own value for a region and compare them before going ahead with the figures they suggest. While I didn’t have the time or equipment to take readings over a year I was able to get solar radiation for two areas from MET Eireann¹². While I obviously would be unable to simply upload all of the raw data I can show some of the graphs I got from my analysis. The data I got was originally in Joules/cm² so the first thing that was needed was to convert this to the kWh/m². How I did this was:

As the data was on the hour ever hour all year round once I had applied my conversion it was simply a case of adding up all of the values to get the total irradiance in the year. The two locations I acquired the data for was Dublin Airport and Oak Park in Carlow. The data was recorded between 2008 and 2010 so I was able to work an average for both areas which I could then compare with the values on the pre existing maps. An example of one of these maps and how the averages I calculated compared to it is:

Solar Radiation Measurements on a Horizontal Surface¹³

From these figures it is clear that while they are not exactly the same as that which has been recorded on the map from Joint Research Centre (JRC) but the map isn’t far off. This however would be expected as the maps would have collated similar information to that which I had but they would have most likely over a larger number of years and locations so taking that into consideration I will use the data maps from the JRC for any calculations done for areas other than the two I have already the information I need.

This was not the only interesting information that could be derived from the data. Due to the detail monthly averages for each month over the 3 years could also be easily attained, the results of which are graphed here below:

From these graphs we can easily see just how much the solar radiation varies over the course of a year from an average of 17 kWh/m² in December to 157 kWh/m² in June which while wouldn’t affect a calculation for the predicted returns on a site but it would have an effect if a certain amount of money was needed each month to cover mandatory costs such as maintenance etc.

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Specifications for a 1MW power plant

With a way of getting the solar irradiance of an area I can now begin to design a power plant using PV solar panels. For this I decided to design a 1MW power plant and calculate the estimated outputs from such a plant. The process I went about to do this was:

• 1. Choice of Panel: For this I decided to go with a 230 Watt-peak (Wp) panel, this is the maximum output from panel when measured under perfect conditions but is rarely ever seen in practical applications. To work out how many panels would be needed to have a plant rated at 1MW we simply divide the Wp of one panel into the max rated output of the plant which gives a figure of 4348 panels needed. For the purpose of the calculations I have chosen a specific make of panel which is an LG polycrystalline solar module which has an efficiency of 14% according to the datasheet for it.¹⁴

  2. Calculate the amount of radiation converted to electricity: As discussed solar panels have quite bad efficiency levels for converting the photons into electricity which can be seen from the maximum efficiency of 14% offered by the LG module using this though the average amount of energy harvested per square metre each day can be calculated as shown:

     1. Solar Irradiance in Dublin Airport is 980 kWh/m² in a year

     2. =>That gives an average of 2.7 kWh/m² a day

     3. If the panels have an efficiency of 14% then they output an average of 381 Wh/m²/day

  3. Area of Panel Array: With the amount of energy that can be absorbed per square metre of panels then it is important to calculate the area of the array. How I did this was I got the dimensions of one cell multiplied this my the number of cells in a module and this by the overall number of modules as shown:

     2. 1. Area of 1 cell = 0.156m x 0.156m = 0.24m²

        2. Area of 1 Module = 0.24 x 60 =1.46m²

        3. => Total Area of solar array = 1.46 x 4348 = 6349 m²

  4. Yearly Output of Solar Array: From this we can calculate the average output each day and for a year as shown:

• • • 1. = 381 Wh/m²/day x 6349 m² = 2,418,969 Wh/day

      2. ~ 2,419 kWh/day

      3. => Average Output of array in a year = 2419 x 365

      4. ~ 882,935 kWh/year

Using the same steps I also calculated the predicated output for the same array if it was in Oak Park and from information given by the JRC map one area that could give the best possible output as far as high radiation values shown is Waterford. These results including that what was shown for Dublin is shown here:

* All values measureed in kWh/m²

It is clear from the table that the best location for the site would be in Waterford but before I go on and use these values for calculations the angle at which the Irradiance measurements were taken at must be considered. So far the measurements looked at have been taken on a horizontal plain but this is rarely the best case to achieve an optimum amount of absorption of photons unless of course you are designing your array to be located at the equator. This makes sense as anywhere else in the world the sun is not directly above the panels but at an angle to the location so an array set up like this will encourage an increase in losses due to reflection. An experiment which I conducted earlier this year was aimed at showing how the varying of an angle at which a panel is placed can lead to an increase or decrease in its output. For the experiment I used a 4.5W polycrystalline silicon panel and a 5W amorphous silicon panel to enable a comparison in response between the panels and also as it was a dull day the idea of the amorphous performing better in low light and shading could be considered. For the purpose of the experiment I only recorded the voltage output of the panel and the intensity of light at which the reading was taken, as I felt this was enough to show any improvement that occurred from a change in angle. An example of the results I recorded can be seen in the table below from readings taken at midday:

I took readings like this from 10 in the morning until 4 when the readings began to decrease due to the reduction in sunlight. With the day’s worth of data I was able to get an average value of the voltage outputted from each panel at the different angles over the course of the day and graph them against the angles at which the voltages occurred to see how they reacted at the different angles, the results of which can be seen here along with the table containing the values of the averages:

From these results it can clearly be seen that there is a peak in the values around 60 degrees which is a little more than you would expect for the time of year as in march normally the panel is at an optimal angle when equal to the local latitude¹⁵ but proving this was not my aim it was simply to prove that there was a noticeable peak around when the angle was varied and that angles smaller or greater than this angle reduced the output of the panel. If repeating the experiment I could record the current being generated to compare the overall wattage being outputted versus the rated maximum to show how much of a difference there is between the panels operation in real world applications versus laboratory conditions. Also by taking more readings at angles between 45 and 60 degrees I could have investigate if setting the panel set at an angle equal to the local latitude gave the best results which is what would be expected in March¹⁵. However some more interesting information that can be extracted from this data is that the effect is greater in the polycrystalline panel compared to the amorphous with it increasing its output by nearly 1.8 volts compared to a change of only 0.8 of a volt but also if the rated outputs are considered the 4.5 Watt panel is meant to output 16V whereas the 5W panel is to output 22V we can see that the amorphous panel is closer to this output than the polycrystalline showing that it may be the case that they work better in low lighting but there is not enough data to conclusively state this from the results recorded for this experiment alone.

Getting back to the angle of the panel though another useful illustration to give further insight into where this peak comes from and why this optimal angle varies throughout the year is shown below. Considering this we can see that if we were to set up your panel to work well in Summer you will reduce the panels output in winter and vice versa. With this in mind it becomes clear that an optimal angle for a panel to be at for good use all year round would be between the optimum angles for winter and summer so neither gets preference. This angle is normally estimated to be equal to the local latitude of where the panel is being installed¹⁵.

Variation in suns path in at different times of year¹⁶

Taking this into consideration then for a solar panel array in Waterford should be angled at around 52° facing south to get the best possible amount of energy over the course of a year. Why south facing has simply to do with Ireland is in the northern hemisphere so if the panel faces south it is facing the direction of the equator where the sun is directly overhead so as it moves from east to west across the sky the panel has the best chance of absorbing the radiation. To see what sort of improvement was possible from angling the panels I got figures from another JRC map which had the solar irradiance on a panel tilted at an optimum angle, not specified on the site what exact angle is but will be assumed that it is the local latitude, and calculated the possible outputs from the panels over a year. With these new values I drew up a table to compare the possible outputs of the three sites including the percentage increase for each site. This table along with the map I got the new Irradiance values from is shown below:

Solar Radiation Measurements on a Surface at optimum tilt¹⁷

It is clear from the table that while the biggest percentage increase is if the site was in Oak Park the highest yield is still in Waterford so considering this I will assume that the site would be set up in Waterford and all the panels would be positioned at the optimum tilt angle.

Before we go on though there are a few more important concepts to be considered before we have a useable figure for the yearly output of the system. So far we have a possible output for the Waterford site of 2962.87 kWh a day giving a yearly output of 1081447.55 kWh however this assumes a perfect system without losses but this would never be the case. In order to take these losses into account I will assume 14% loss as suggested by PVGIS as a general inefficiency level for PV systems, examples of where losses can occur are in cables, and inverters¹⁸. Taking this percentage loss into account then the output used for the calculations of the return from the system will be starting at 930044.89 kWh.

There is one final limitation to consider and that is the fact that the output of the modules will reduce over its lifetime and while they have been known to function for 30 and sometimes 40 years they do not function as well as when first out of the box as you would probably expect. Looking at the datasheet for the LG panel it offers an output warranty of 90% for a 12 year old panel up to 24 year and from 25 years on it offers a warranty of 80%¹⁴. This means that the outputs that could be expected over the modules would be assuming the lifetime of the solar module would be 30 years:

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Land requirements for 1MW plant

Next thing you would need to set up a site is land to set it up on. The requirement for this has been estimated at four times the area of the solar module. It isn’t simply four times the area of the array we have used so as this was calculated using the area of each cell and the module would be greater than just the area of 60 cells. According to the data sheet the module is 1679mm long and 993mm high this gives a module area of 1.6m2, assuming an area of 4 times this and there is 4348 panels then a 1MW power plant would need at least 28,410m2 of land.

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Capital Costs

Before we go on to look at the possible returns from such a site first we will look at the costs involved in building it. With this information it can then be predicted how long before the site would pay for itself and what profit is viable. I’ll do this by starting with the cost for the panels and go from there:

Solar Panels: As mentioned for my analysis I have chosen to use an LG Polycrystalline Module, the LG230 P1C, which I found on a site that offered the panel at €379.49 for orders over 20 modules with a shipping cost of €25 this works out at a total cost of 1.76 euro per Watt (€/W)¹⁹. So assuming no further discounts would be available on large orders then the cost for the panels would be roughly €1,760,000.

Inverters: There is not much point in producing all this energy if it can’t be used and as the energy that has been spoken of so far is DC as this is what PV panels output then to connect to the grid an inverter will be needed. The price of the equipment varies but the average in Europe is 0.53 €/W²⁰. This means to provide enough inverters for the array it will cost a little more than €510,000.

Cost of land: Next we will consider the cost for the land needed to construct the site on, for this we need to find out how many acres of land 28,410m² is as land is normally sold in acres. This conversion is simple enough 1 acre is equal to 4046.9m² so that means just a little more than 7 acres will be needed. The price for land can vary but a good example of the possible cost would be the 14 acre plot that can be seen here. This means that the cost would be around €10,000 per acre meaning the land costs would equal €70,000.

Connection to the Grid: Next there are the costs involved in connecting to the grid as this of course would not be free. While there is no sites such as this set up in Ireland there is a number of wind farms and due to the increase in applications for grid connections of such sites a group connection processing scheme was set up in December of 2004 to deal with renewable energy connections. This is where all projects that are due to be completed by a certain date are grouped together and processed as a group rather than on an individual basis. These groups can then be subdivided between transmission and distribution generators and further divided in these groups but the idea of the group scheme means that the overall affect of the new connections will have on either the transmission or distribution network can be assessed a lot easier than if the sites are addressed separately. This doesn’t affect the quality of service and feedback given individual sites it just means time taken to process applications can be reduced as can the integration of all the sites to the network and allows possibility of too many connections being made to an area where the demand doesn’t need it to be addressed.

For a site of the size being looked at here it would most likely be connected to the medium voltage (MV) infrastructure, normally at a voltage of 10kV at the moment but maybe 20kV in sites that have been updated, of a 38kV ESB substation which is part of the distribution network. It definitely wouldn’t be connected to the transmission network however as it is recommended that the capacity of the plant should be over 20MW for this²¹. Assuming that some shallow or direct connection work would be needed then application fee for the group scheme would cost €8,185²². This doesn’t include the licences needed assuming your application is successful but this is only another €70²³. The most costly part of the process will however would be the cost of installing the equipment needed which assuming we take the site in Stradbally could amount to roughly €750,000. The breakdown of the figure is outlined in the table of costs at the end of this section but what it includes is:

• • Installation of a cubicle in a station where the power outputted from the station can connect into an ESB substation

  • Construction of overhead lines to transfer the energy between the site and the nearest 38kV substation which would be in Dungarvan which is 13km away according to the information on the real estate agents website. Underground cables could be used but they are more expensive and result in civil works which would further increase costs

  • Meter to record the energy being exported to the grid

  • Protection and communications equipment involved in ensuring if and when there are faults in the line they can be dealt with safely

All figures used in these calculations were taken from the ESB Standard Prices for Generator Connections 2011²⁴ and the guideline for the calculation was taken from an example in a guide produced by Sustainable Energy Ireland called “A Guide to Connecting Renewable and CHP Electricity Generators to the Electricity Network”²⁵.

Operating and Maintenance Costs: An important part in making sure that your panels and other equipment last as long as possible and are able to produce the maximum amount of energy they can then it is imperative that they are looked after. To ensure they are looked after then money is set aside for O&M costs, examples of the kind of things involved the table below outlines possible tasks and how often they may be needed:

Breakdown of Possible O&M Costs and Frequency at which they are to be done²⁶

As there are no sites in Ireland to have a look at to see what of these task may be applicable or not I have taken the estimated values given in the survey done by the Electric Power Research Institute in the US and converted them to euro to give a rough idea as to what you would expect them to cost each year. The table breaks done the costs as follows for panel such as the ones that would be used in this site:

Estimated Costs for a crystalline array²⁶

Converting the total to euro we get O&M costs of 36 €/kW each year, therefore for this site the yearly O&M costs would be €36,000. Assuming a life time of 30 years then the total cost can be estimated as €1,080,000.

An overall summary of all of the costs mentioned above and an estimated cost per watt has been calculated in the table below:

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Return on Investment

Having looked at how much the system would cost taking in most if not all of the important factors now we can look at the way in which the array can make money to repay these costs. There are two main sources of income for renewable energy plants:

REFIT: This is the Renewable Energy Feed in Tariff which is paid to the generator as a way of supporting them and aid in the increase of renewable energy sites in Ireland. While there is not tariff currently for solar energy the table below gives an idea of the kind of levels offered for other forms of renewable energy:

Example of shading on a tracking system³⁰

Storage: Another possibility for improving the system is the addition of storage to it, the advantages of which we will look at later but first two examples of the type of storage available:

· Battery Storage: This is obviously the first storage possibility that people would think of as well you think stored energy you of course think battery but how feasible is it really? In my opinion not hugely. Why I think this wouldn't be the best option is that I have been in battery rooms in substations and seen rooms devoted to batteries that are simply used to power the basic operations occurring on the site nothing to do with the power being pumped out of it so the land need to house this amount of batteries would be colossal. Also if it is a Lead-Acid battery then maintenance on each battery would involve cell testing to ensure the batteries are holding their charge which would take a long time which would drive up O&M costs. If however you where to go with grid capacity batteries such as the one shown in the image below which was installed in Charleston, West Virginia as a way of dealing with the varied wind energy output then you are looking at a cost of $4 million³¹ or just over €3 million for a 1MW battery not including shipping and installation costs of a monster battery such as this which could easily double the cost of a site such as this.

Turlough Hill³³

Having looked at two storage options and pointing out the main downfall of each being the increased capital needed I will outline what I think the main advantages and disadvantages of each and leave it up to you to decide if I am right or not to consider them to be possible improvements or just ideas that would cost more then they are worth:

Direct Connection

Advantages:

• • • No increase in capitol costs

    • Flexibility of location

    • Building integration possible in built up areas

    • Money being made as the energy is produced

Disadvantages:

• • • Output from site varies a lot over the course of a year

    • No scope for output at night which is a huge problem in winter as peak times to sell energy would late when there is no sun

Storage

Advantages:

• • • Best price for the energy produced can be achieved rather then having to settle with the current price as the energy is produced

    • A better quality of energy can be sent to the grid with regards to consistency of the sites output

    • Capacity payments are made to generators that have the ability to produce electricity when needed by the grid

Disadvantages:

• • • The overall size of the site is increased meaning the location of the sites are restricted

    • Will result in a increase in capitol costs

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Conclusion

Having completed the study and designing a possible site even with best estimates and optimistic revenue values it is clear why sites such as this hasn't taken off in Ireland. What is also clear is that it has not just got to do with the generating capacity or the cost involved in setting up the site, it has also got to do with the lack of backing from the government for such infrastructure. If we compare my optimistic REFIT of 10c/kWh to other european countries, shown in the table below, then even if offered the lowest rate which is seen in Spain the profit from this could double the money made to €2.8 million which would equate to over half of the predicated capitol costs being recovered in the 15 year the scheme is offered for in the first 15 years without the money being made from the selling of the actual electricity. However until better support is set out or advancements are made with the technology then photovoltaic solar is an infeasible energy generation method for utilisation in Ireland.

Table outlining schemes in Europe to subsidise PV generation¹⁵

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References

1. Structure of Panel, URL: www.reuk.co.uk/How-Do-PV-Solar-Panels-Work.htm

2. Layer Sturcture, URL: http://specmat.com/Overview%20of%20Solar%20Cells.htm

   1. Lecture Notes: Horan, K., Daniels, S.; EE403 – Semiconductor Devices

3. http://www.solarserver.com/knowledge/basic-knowledge/photovoltaics.html

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6. http://thecoolgadgets.com/wp-content/uploads/2009/08/srs-solar-roof-tiles-front.jpg

7. Martin A Green; "Crystalline and thin-film silicon solar cells: state of the art and future potential", Solar Energy, Volume 74, Issue 3, March 2003, Pages 181-192

8. http://image.tradevv.com/2008/04/26/leichao627_795551_600/156-156-polysilicon-solar-cells.jpg

9. Advances in crystalline silicon solar cell technology for industrial mass production, NPG Asia Mater. 2(3) 96–102 (2010)

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13. http://www.lg-solar.com/en/business-resources/download/Datasheet_Multi_US.pdf

• 1. Lecture Notes: http://elm.eeng.dcu.ie/~ee535/

14. http://harvestenergysolutions.com/img/pages/69786093430594.gif

15. http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_solar_optimum_IE.png

16. http://re.jrc.ec.europa.eu/pvgis/apps4/PVcalchelp_en.html

17. http://www.solarshop-europe.net

18. http://www.solarbuzz.com/facts-and-figures/retail-price-environment/inverter-prices

19. http://www.cer.ie/en/renewables-connecting-to-the-network.aspx?article=f7c88c3f-26d5-4878-8850-a08ff7e2a359

20. http://www.cer.ie/en/renewables-connecting-to-the-network.aspx?article=68c8fc68-4eab-4276-a7b8-4aa5113064f1

21. http://www.seai.ie/Publications/Renewables_Publications/connecting_RE_and_chp_to_network.pdf

22. http://www.esb.ie/esbnetworks/en/commercial-downloads/Standard-Prices-for-Generator-Connections.pdf

23. http://www.seai.ie/Publications/Renewables_Publications/connecting_RE_and_chp_to_network.pdf

24. http://www.smartgridnews.com/artman/uploads/1/1021496AddressingPVOaMChallenges7-2010_1_.pdf

25. http://www.seai.ie/Publications/Statistics_Publications/SEI_Renewable_Energy_2010_Update/RE_in_Ire_2010update.pdf

26. http://www.iwea.com/index.cfm/page/windenergyandtheelectricitymar

27. http://www1.eere.energy.gov/solar/sunshot/pdfs/dpw_white_paper.pdf

28. http://howsolarworks.1bog.org/solar-trackers/

29. http://news.cnet.com/8301-11128_3-20012597-54.html

30. http://www.esb.ie/main/about-esb/turlough-hill-station.jsp

31. http://www.esb.ie/main/img/turlough-hill-1.jpg

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