Technical considerations for solar carports

Many will be aware of the 2018 report from the Intergovernmental Panel on Climate Change (IPCC) which made it clear that we have around 12 years to reduce CO2 emissions (global net) by 45% in order to limit global warming to 1.5°C, and avoid catastrophic consequences. This serves as a stark reminder of the need to decarbonise the two sectors which are emitting the most greenhouse gases (GHG) into our atmosphere: the transport sector, and the electricity supply sector. 

The most successful current approach to reducing emissions from the transport sector is to electrify transport systems, which is driving an increased reliance on decarbonisation of the electricity supply sector. Electric vehicles can lower GHG emissions, and also promise to lower the lifecycle costs of transportation. 

With this in mind, it is not difficult to understand the need for integrating Solar Carports into our transport network. The basis of a Solar Carport is covering parking bays with solar PV canopies to supplement/meet energy demand on site. This can be applied wherever there is a requirement for, or an existing carpark, for example a park and ride hub. By adding battery energy storage systems (BESS) and EV charging to the solar carport, we can realize even more climate benefits. We lay out the steps to designing this system below.

Solar PV generation offers a low-carbon alternative to burning fossil fuels. Alongside solar well-known environmental credentials, it is already in some cases the cheaper alternative to many thermal plants, making solar an increasingly viable option for investors. A booming market in Asia, improved manufacturing techniques and worldwide deployment on a large scale are just some of the factors ensuring that the cost of solar PV will continue to drop in the next 3-5 years. 

Battery Energy Storage Systems (BESS) can be used to great advantage when integrated into variable renewable energy generation systems. As the generation profile of solar and wind sources cannot be guaranteed to match the load profile, the consumer may find themselves without energy when required or vice versa if renewable sources are used alone. 

However, if the energy can be stored when excess energy is produced, it can be used when generation does not meet demand and economies can be realized at times where electricity from the grid is cheaper than peak times. Therefore, BESS can optimize the usage of power generated from the solar PV modules. As with solar PV, capital and operational costs of battery systems are dropping due to large-scale investment and mass production at a global level and are forecasted to do so for the next 3-5 years. 

EV Charging Points are essential in moving to a low carbon electrified transport infrastructure. Most new infrastructure projects in the UK with any links to transport including EV charging stations are future proofing their designs by providing the conduit and connection points. This will allow for easy and quick retrofitting of the charging equipment and cabling in the future. 

EV charging points are available in a range of sizes, allowing various charging speeds for vehicles of all sizes. This opens up potential for providing a supply for an all-electric bus fleet which is particularly relevant to park and ride Carport configurations. The low operating voltage of charging points (up to around 800V for bus charging points) allows integration into solar PV and BESS solutions without the need for expensive conversion equipment that would usually be required to feed renewable energy back into the grid.

1. Load Analysis

In order to review the technical suitability and the financial implications and carbon-saving potential of any solution, the energy demand and load profile of the carport need to be considered. This means identifying how much energy an asset requires and when. A load profile from EV charging points and/or other electrical loads (lights, AC, elevators, etc.) is determined and an aggregate energy demand over the day, month and year can be calculated. The number and type of vehicles, as well as the charging time requirement, help to determine the appropriate sizing and specification of the EV charging points.

2. Solar Canopy and Associated Equipment

The location of the carport and parking bay layout are important variables when determining the best canopy design option. Local weather conditions affect wind and snow loading on the canopies and in turn the foundation and structure design. The parking bay layout influences the direction of tilt on the canopies which should be designed to optimize yield. Aesthetic considerations are also important and can be accommodated in new designs and in most retrofits. Solar PV modules and associated equipment are identified at this stage. 

3. Energy Yield Assessment

Once the solar PV layout and equipment have been specified, an energy yield assessment is completed. This determines the total energy yield from the solar PV modules that can be fed into the system as well as the hourly, daily, and monthly generation profile.

4. Battery Sizing

Having profiled both the carport’s load and the solar PV facility’s generation, the two can be analyzed together to anticipate the extent to which the solar PV facility is likely to meet the demand, whether there is sufficient excess energy at points throughout the day to justify the use of a battery and if so, what size should the storage system be.

5. Energy Management System

In order to meet the energy demand using the most economic and lowest carbon source mix of generation from the solar PV and BESS facility (and the corresponding level of supply from the grid), an appropriate energy management system needs to be specified. This can be driven directly by the BESS management system capable of dispatching the required load through algorithms aiming at maximizing solar absorption and minimizing overall cost of electricity.

Establishing funding and planning for the installation of solar car ports should follow the analysis discussed above. Inputs from the initial technical studies can be used to:

• develop a business case for funding and inform grant applications;
• be fed into planning applications;
• determine carbon savings; and
• establish revenue inputs to financial modelling for the project.

Renewable generation and BESS are essential components in the challenge to decarbonise our transport and electricity generation sectors and in order to deploy this technology, WSP can do their bit through the provision of both technical and commercial analysis.

Expect to see a solar carport arriving at a city near you soon…

Alex Rout, Renewables Engineer, WSP