“You Can’t Eat Solar Panels” – The Case For Rooftop Solar
There’s a little island off the Central American coast called San Andres where the water is warm, the beers are cold, and the electricity is expensive. Really expensive! It’s about five times as much as the US national average which is quite a burden for the local residents. Caribbean islands generally don’t have the natural resources that other mainland nations do, and San Andres is no exception, importing 37,000 gallons of diesel from abroad each day to keep the lights on. All these factors increase the price, and are part of the reason that the little island has made a pledge to move towards 100% renewable energy as part of the Carbon War Room’s 10 Islands Challenge.
You Can’t Eat Solar Panels
On a recent visit, Chad Nancarrow of DNV GL Renewables and I were in a town hall meeting discussing options for renewable energy with the local residents. We had flown down to help assess how the island could reduce energy use and install renewables to become self-sufficient. Chad was in the middle of outlining the few options for large-scale wind and solar facilities when a local Rialto spoke up:
“I don’t like it! You tell us you’re going to take our land and install these power stations. We won’t be able to farm these areas anymore, or use that land for our cattle to graze. I know we need clean energy, but we can’t eat solar panels! Put it on the roofs!”
You know what? He’s got a point. It’s often easier to look into installing large scale wind and solar power plants due to economy of scale and the ease of installing by the Megawatt. After all, a MW of solar takes up about 4 acres of area and it’s awfully difficult to find a roof that large outside of the Tesla Gigafactory. However, there are acres upon acres of empty roof space just sitting there wasted. The land has already been altered in the name of development, and the only thing the wasted sun is doing by hitting the roofs is adding to the air conditioning load of the building and adding to the heat island effect that plagues our cities.
A roof on a home might only net you 10kW, and a roof on a school might yield 100kW. Add every house and school in San Andres, The Bahamas, or the United States and you’re getting somewhere. In addition, every square foot of energy generation we can keep off the ground is a square foot that can be used for parks, homes, or schools.
Land, a Limited Resource
We’re blessed with enough empty land in the United States that utilizing inland areas for wind and solar farms is worth it. Trust me; I love to see 100 MW of renewable generation as much as anyone, however, as the population grows, we might not be so lucky. Places like San Andres, the Bahamas, Germany, and England don’t have the luxury of ignoring rooftops on the path to a renewable future. They need to leverage every square foot of rooftop and then some to make up for what little extra land is available. In preparation for a continually growing population, the US needs to think ahead as renewable generation is planned. Places like California with its requirement for a solar-ready zone are already on the right path, but they will need to make sure every single roof is occupiable, vegetated, or renewable to ensure parklands are maintained and acres are available for our grandchildren.
One big benefit of distributed rooftop solar is that the power is generated where it is used. It helps minimize losses due to transmission, and, if done right, reduces the overall cost of the grid by reducing the need and scale for new transformers. This will be especially important as our vehicles largely turn to electric drivetrains. One out of every 130 registered cars in CA is an EV today, and we are slated to pass the 1% mark by the end of the year. This is putting huge strain on the grid, as Sacramento Municipal Utility District (SMUD) has been finding. Rooftop solar mixed with storage is a way to combat this issue.
On the flipside, it is possible to site large wind and solar farms on major transmission lines, allowing an unsurpassed ability to send those electrons across the continent. For instance, the decommissioned San Onofre Nuclear Plant is a perfect location to add a large-scale solar system considering the immediate access to large scale transmission. Doing proper grid integration studies is the key to determining what areas should be targeted for farm size systems in land-poor areas.
All the solutions are positive, and any new renewable generation installation, large or small, is a benefit to society and the right step forward. However, roof area is free area, and when planning for a massive change in our generation systems it is important not to be too blinded by a focus on progress to take a moment and consider the precious square miles of land we call home.