As part of our work on decarbonising the built environment (including our Spectrum of Decarbonisation), we have been thinking about the role technology can play in accelerating change. In this article, we look at on-site solar, which has a critical role to play in reducing the operational emissions of buildings. How can technology help make it more efficient and reliable?

If we aspire to buildings that are True Zero in operation – that is, zero emissions without the need for offsets – maximising the use of on-site renewables is a must.

Off-site renewable energy generation comes with ongoing risks around the long-term resilience of supply, and the traceability of some renewable energy contracts. Whereas if you can produce enough energy from on-site renewables to meet the building’s entire energy consumption requirement, you’re less reliant on the grid (making the building more resilient and cheaper to run) and your building’s carbon emissions will be negligible.

On-site solar is proving to be a powerful and increasingly cost-effective way of doing this. The cost of solar photovoltaics has fallen by about 90% in the last decade*, driven by economies of scale, manufacturing efficiency, and technological improvements. Per Wright’s Law, costs fall by around 20% every time global cumulative capacity doubles. During our lifetime, solar power has gone from being from one of the most expensive electricity sources in the world to one of the cheapest.

On-site solar does have its challenges, however. Up-front cost is clearly one possible barrier. Another obvious one is space: it’s not always possible to install enough solar PV to meet the building’s energy needs (especially for particular types of building, and/ or particular types of tenant). Weight can also be an issue: an existing structure might not be able to support the amount of panels required.

But even when installation is viable, that’s only half the battle won. A number of factors can reduce the output of solar PV systems in operation, including shading (from nearby trees or buildings), soiling (accumulation of dust, dirt and debris), technical problems and environmental conditions. Unless they’re spotted early and fixed, these issues can lead to substantial system losses. The extent of this varies significantly from country to country, but on average, most commercial PV systems probably lose 10-20% of possible output annually (according to the IEA, soiling alone accounts for an average 4-7% loss globally**). For real estate owners, that has a very obvious impact in terms of energy costs and carbon emissions.

This is where technology has an important role to play. There are now systems that offer real-time monitoring and predictive diagnostics for solar PV systems – benchmarking generation against irradiance-adjusted expectations (i.e. how much the system ought to be producing in the current weather conditions). This doesn’t just allow for more transparent measurement and reporting. It also detects faults earlier and diagnoses solutions – so O&M (operations and maintenance) becomes much more responsive and efficient. All of this improves uptime and minimises costs, making the economics of solar installations more attractive.

Clearly this kind of monitoring software does add to the up-front cost. But if it ensures that solar PV systems actually deliver to their full potential, there’s a compelling value case. Indeed, some providers are leaning into this by offering financial guarantees or compensation to owners if system output falls below forecast – further de-risking the investment.

Either way, it’s a good example of how technology can help accelerate the process of reducing operational carbon emissions from the built environment – by making on-site renewables more cost-efficient.

Of course there’s another big challenge with on-site solar that we haven’t mentioned: how to manage the mismatch between demand (when the building needs energy) and supply (when the sun shines). A key part of the solution to this problem of intermittency is battery storage and management – but this comes with a number of additional challenges. We’ll be looking at how technology can help tackle some of these next week.

* Solar panel prices have fallen by around 20% every time global capacity doubled – Our World in Data

** Fact Sheet Task 13/16 Soiling