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Nov 11, 2024

How system design optimisation for solar farms can support the UK's net zero target

The United Kingdom has set a Net Zero target to reduce greenhouse gas emissions by 2035. The plan is to increase solar capacity fivefold to 70 GW by 2035. This bold target presents significant

The United Kingdom has set a Net Zero target to reduce greenhouse gas emissions by 2035. The plan is to increase solar capacity fivefold to 70 GW by 2035. This bold target presents significant challenges and remarkable opportunities for solar companies.

BELECTRIC is one of Europe’s leading service providers for developing, constructing, and operating solar power plants. With over 23 years of experience, the company is also a leader in solar and battery storage solutions.

In this piece, I provide insight into how BELECTRIC’s approach to economic optimisation of utility-scale solar farms leads to more area-efficient system designs, supporting the UK’s Net Zero goal.

Few different components are needed to build a ground-mounted photovoltaic system, but many of them. Relevant parameters such as row spacing or tilt angle are defined once, as are modules and other elements, and then scaled across the entire plant. This suggests that small changes in the components and design parameters can significantly affect the cost and yield of the overall system.

How many possibilities are there for building a ground-mounted photovoltaic system? More than you would expect. Looking at different tilt angles, row spacing, a range of DC-AC ratios, and different substructure and module types, you very quickly end up in the five-digit range for relevant system design combinations.

The decisive question arises as to the objective of the optimisation. The levelised cost of energy (LCoE) is a value focused mainly on cost optimisation, not on actual expected revenues. When actual revenues are considered, a different conclusion is usually reached. Although certain decisions may increase the cost of electricity, the higher cost pays off in the long run. This is because it is possible to achieve revenues per kilowatt-hour that are higher than the cost of electricity. Therefore, the LCoE as a key performance indicator is not relevant for investment decisions.

In addition, a phenomenon that can be well described as the area trap often occurs in optimising ground-mounted plants. General studies on electricity production costs frequently claim that an infinite amount of land is available. A specific price per hectare is then assigned to this area. When comparing solar trackers to fixed-tilt systems, it is, for example, assumed that the tracker system will simply incur higher lease costs due to its higher land requirements.

However, in the real-world development process, things are mostly different. The project developer secures as significant an area as possible and considers which system design they want to realise. The area is, therefore, not variable. When considering the real case, the result differs significantly from the former comparison, which would have calculated a tracker plant with the same output as the fixed-mounted plant that merely requires more land.

Let’s look at the metrics investors typically use to evaluate future cash flows. These are not the cost of electricity, but the net present value (NPV) and the internal rate of return (IRR). There is often a conflict between achieving the highest possible NPV and the highest possible optimal return on investment. In other words, with one system design, the NPV of the project would be higher, but the IRR would be lower, while with another system design, the tide turns. In such cases, we at BELECTRIC naturally let our customers decide, but almost without exception we recommend optimisation to the maximum NPV. This value is methodologically more reliable and more robust regarding changes in total investment costs.

With the various system designs established on the market, it is possible to optimise the business case via the specific yield and costs and the investment volume. This lever is not taken into account when particular parameters are considered on their own (IRR, LCoE). This is another reason BELECTRIC recommends looking at the NPV of all relevant system design combinations for each project.

By doing so, we see patterns and tendencies deviating from the industry’s current design standards. We see a trend towards more area-efficient systems with lower row spacing and tilt angles that can apply more MWp of renewable energy per hectare. To reach the targeted solar capacity, our society will have to consume less land in the considerable range of 15-20%. Plus, the investors are happy to see higher profitability for the projects.

Studies show a link between extended row spacing and biodiversity optimisation. A “sunny stripe” between the rows seems to increase the diversity of flora and fauna in a PV power plant. However, row spacings for biodiversity would increase land needs by about 30%. It comes with a significant downside to the land efficiency of PV power plants. But when solar farms replace intensive agricultural activity using herbicides and pesticides, biodiversity always wins – regardless of the row spacing. This applies particularly to the environmentally friendly design of the solar farms, to which we at BELECTRIC attach great importance. We believe it is crucial to transform as little land as possible into PV plants to reach overall renewable targets. And that is possible all whilst fostering biodiversity.