Land based solar installations

Steve Gummer looks at the opportunities that solar farms offer local authorities.

This year under the Green Steve’s programme we are going to focus on two key areas, the first of which is solar energy. 

The intention is to focus on solar PV projects and take a deeper dive into the issues involved and how to steer a successful project through delivery. As the energy crisis last year bit deeper, many more local authorities looked at the potential for solar and these papers are intended to assist them in formulating plans and driving them forwards.

The first paper in the series looked at Government policy and its importance in retaining the UK’s leadership role as well as giving the markets confidence to invest in the green agenda. The second paper looked at the other end of politics i.e. strategy at the local authority level. This is where real life projects are forged and brought into delivery.

This third paper in the series now moves to more detail about land based solar installations, in other words solar farms. These are to be contrasted with buildings based installations, which will follow next in the series.

Solar Power

Solar power is immensely powerful. Jeremy Leggett in his seminal book The Solar Century noted that if we capture only a tiny fraction of 1% of the sun’s irradiance we could provide more power than the whole world currently needs. The sun has been used for thousands of years for a variety of purposes, including heating homes and water. It also founds the root of many other forms of renewable energy including biomass, geothermal and wave & tidal.

Local authorities have over the last decade developed a growing interest in photovoltaic power where the sun’s rays are turned into electricity and the potential of using land for developing solar farms. Indeed, many local authorities now have either aspirations in this direction or actual plans in train.

Key Factors

There are a number of factors in photovoltaic power that need to be outlined. These include how electricity is generated, the factors that determine the level of power and the difference between power and energy.

The Science

Essentially, the photovoltaic process is founded on the ability of a semiconductor to covert light into electrical energy.

The process works when a semi-conductor material absorbs light and positive and negative electrons are released.

These are then extracted from the semiconductor as electric current. Most PV cells are made from silicon, which is readily available, being able to be extracted from sand, one of the earth’s most available commodities. This effect takes place in a solar ‘cell’ that is usually very small and fragile. The electricity generated by a single cell is very small, but when connected together in the form of a solar panel, this output is greatly increased. The cells are also protected by being sealed in a weatherproof module consisting of a glass front, aluminium frame and protective cover.

Irradiance

The impact of the sun’s rays on the earth is called irradiance. Levels of irradiance will differ, depending on where a person is in the world. Naturally, some parts of the world are warmer and sunnier than others. Even though solar power does not work directly from the sun – but from daylight – this will affect the level of energy that can be captured. Regard needs to be had, therefore, to the level of irradiance available for a solar project. It is often stated – erroneously – that the United Kingdom is “not sunny enough” to justify solar power.

There is a map of the UK with the irradiance levels across the country illustrated upon it. This shows that the South West and South of the country are the best places for solar power, hence the level of activity seen in Cornwall, Devon and the south coast areas from 2010 onwards. However, solar power works perfectly well in the Midlands and the North, albeit with slightly lower levels of irradiance.

The average irradiance in the UK is 800 kWh per annum of electricity, per kW of solar PV installed. There are six factors that determine how much power will be possible from any particular area.

The Six Factors

The purpose of a solar PV system is to translate as much daylight into electrical energy as possible. There are a number of factors that will affect this purpose, the most commonly quoted of which is a south-facing orientation.

The six factors are as follows:

• Latitude – how far the area is from the Equator. There is not much a local authority can do to alter this factor!
• Air mass – essentially the quality of the air that the daylight passes through to get to the solar panel (dust and gas particles will affect this)
• Cloud cover – less power will be generated where there are not clear skies
• Shading – an obvious problem, caused where the light cannot get directly to the solar panel. Could be due to topography (hills and valleys) to buildings (chimneys and roof based equipment)
• Tilt of the panel – in the UK the optimum is between 30 and 40 degrees, depending on latitude (lower in the South, higher in the North)
• Orientation i.e. which way the panel faces, generally South being the optimum

How well a system performs will be determined by these factors. What is more, they can all be predicted in advance as the position of the sun during its particular passage on any given day is set and does not change.

Current

The electrical current that is created in the photovoltaic cell and subsequently extracted as a current, is direct current (DC) not the alternating current (AC) on which the normal mains supply in the UK operates. It is therefore necessary to pass this current through an inverter, to convert it to AC supply.

Power and Energy

It is necessary to distinguish the two concepts of power and energy. PV systems are described using their maximum power, for example 5 MW for a commercial sized solar farm. That is the maximum capacity at which the system can work and represents the rate at which energy is created. The more important element, therefore, is energy, which is the actual output in units of the installation.

So a 5 MW solar farm in Cornwall might deliver 5,000 MWh (or 5 million kWh) of energy per annum. The reason that energy is the key element, is that it is this number that feeds into the financial and business case modelling which provide rates of return on the capital employed to install the system in the first place. Moreover, if the energy is to be used by the Council itself, it will be aware of how much energy it requires to run its services.

Solar Farms

A solar farm is nothing more than an area of land that is used to host solar panels as part of a renewable energy installation.

Size and Capacity

There can be no doubt that solar farms are getting bigger. In the early days after financial incentives were introduced by the Government, solar farms of 5 MW started to emerge. Over time it was realised that economies of scale are in play and so solar farms of 50 MW started to emerge. Now, there are significant numbers of solar farms of over 300 MW – 600 MW, which qualify as Nationally Significant Infrastructure Projects (meaning the planning decision is taken by the Government, not the local planning authority) and which cover huge tracts of land.

Components

A land based installation is comprised of the following elements:

• Solar panels
• Racking
• Cabling
• Inverters
• Metering
• Grid infrastructure, supply point, transformers etc.

Construction of solar farms is surprisingly straightforward. The land is prepared, if necessary, then piles are driven into the surface, racking is attached to the piles, solar panels attached to the racking and cabling run along the bottom edge. The cables run to the inverters, which are usually in cabinets (often shipping containers) and then the grid supply point and infrastructure.

Type of Solar Panels Used

The main issue with solar farms in the UK is the size of the array and whether to choose static panels or tracking systems. Arrays can be any size within reason, for example, 100 standard sized panels on a platform to form an array; or racks that are only one panel high, in portrait formation, but extend for hundreds of metres in length. This is mainly a commercial and design decision, but may have planning implications.

The choice of fixed or tracking systems is more interesting. Tracker systems come in two varieties – East to West (or horizontal tracking systems) or up and down (vertical tracking systems) or both. The idea of the system is that it moves with the sun during the day and therefore maintains the absolute maximum orientation and/or angle for as long as possible. This can increase the efficiency of the solar farm by up to 20%. As the position of the sun is always predictable in advance, such systems can be programmed very accurately.

However, tracking systems in the past have been considerably more expensive than fixed panels. One of the main advantages of solar PV is that there are no moving parts and there is therefore very little maintenance. Tracking systems, by definition, introduce moving parts and a level of maintenance complexity that would not otherwise exist. This is therefore an important decision. The general view of the solar industry in the UK was traditionally that tracker panels were not worth the extra cost, bearing in mind the additional efficiency that they deliver in this climate, but this is clearly changing. The leading proponents of tracker panels in the UK has been the company Gridserve, which has developed some large land based sides, such as the 30+ MW sites developed for Warrington Borough Council in York and East Riding, which both included horizontal tracking panels.

Interestingly enough, the Gridserve developments also featured bi facial panels which are double sided solar panels, where the underside of the panel also collects irradiance and generates electricity. These are becoming more popular and are normally fitted with the ground surface being designed specifically to provide a better reflection of light, known as the Albedo effect. Apparently, some plants are better at this than others!

Other Issues

Other issues for solar farms, include security, metering and grid connection. On the security front, it is relatively easy to steal a solar panel from racking but the sites are usually rural and the value of panels is now much lower than it was as prices have tumbled so this is surprisingly rare.

Security systems include fences and CCTV and have proved sufficient to reduce the risk of theft. Security elements will also have planning implications, although there is normally an alternative to a six feet hight fence, such as a natural thorn hedge, or to a shipping container for inverters, such as a stone hut (as in the National Parks). These solutions are preferable to the planning authority and can be equally effective.

Metering will also be a little different for solar farms, where the supply of electricity is all being transmitted into the national grid. Some form of meter housing is also required, although normally combined with the inverter and other infrastructure.

Projects

For a solar farm project to be contemplated by a local authority, it needs the following components:

As such solar farms are ideal for local authority development because they are large landholders, have a deep understanding of what is suitable under local planning and can raise finance, such as borrowing from the Public Works Loans Board. Grid connectivity remains a problem, as it does for all other potential developers of solar farms but this is not insurmountable.

Solar Farms or Buildings Based Solar?

Whether a solar farm will be suitable for a particular local authority will depend on its motivation. Land and buildings based solar differ considerably, despite both being effectively the fitting of solar panels. Buildings based systems are often part of a larger asset management strategy, which may also include energy efficiency works or the like. The Council might benefit from solar as part of a wider programme or fit solar PV as part of a retrofit contract for green improvements. By definition, such work can be at any scale and many small installations have been completed of this type.

Land-based systems are normally part of a different strategy. This time, it is more low carbon energy that is the motivation, although such projects will normally deliver both income generation and carbon offsetting benefits as well. These developments are often linked to an economic development strategy, with the energy being provided to the Council itself, or to promote economic growth in the area. A good example of this might be a facility near an industrial or commercial park, where jobs can be created and businesses attracted to relocate. By definition, freestanding solar PV installations tend to be large, possibly very large, and therefore are quite different in nature.

Which type of development is right for which authority depends entirely on the nature and position of the Council and its strategy. The wider strategic issues were considered in [paper 2 in this series] and it is emphasised there that the Council needs to be clear what it wants to achieve from any development.

Buildings based solar installations will feature in the next paper from the Green Steve’s.

Conclusions

Solar PV is booming, which is fortunate for the Government as it has now set a target of 70 GW of solar energy by 2035 (there is currently 15 GW).

Solar is one of the most established technologies and there are many examples of local authorities that have developed or purchased solar farms.

As time passes under climate emergency or climate change action plans, greater progress has to be made towards Net Zero and bearing in mind the fact that solar costs continue to fall (and that solar energy can be enhanced still further by the addition of battery storage) this explains why there is such interest in this area from local government. Such developments are within the grasp of every local authority and it is vital that Councils look carefully at this area.

Steve Gummer is a Partner at Sharpe Pritchard LLP.

As part of Sharpe Pritchard's commitment to helping local authorities innovate in the green space, infrastructure and energy partner Steve Gummer has teamed up with Steve Cirell, a Solicitor and Consultant who independently advises local authorities on climate change and renewable energy to produce a series of thought pieces about what local authorities could be doing to further the green agenda. We hope you have enjoyed reading the third in this series and for more please visit our Green Goals web page and follow us on LinkedIn.

For further information, please contact Steve Gummer, on 020 7405 4600.

This video is for general awareness only and does not constitute legal or professional advice. The law may have changed since this page was first published. If you would like further advice and assistance in relation to any issue raised in this article, please contact us by telephone or email This email address is being protected from spambots. You need JavaScript enabled to view it.