Recent letters and articles in the Gazette have made competing claims about the amount of solar that can be placed on the built environment. Some say that we can fit all the solar panels we need on buildings, parking lots, and similar locations. Others say we will need to use our fields and forests for ground-mounted solar. Can we build the solar we need for our clean energy future using only the built environment? The answer to this question can frame our response to future large-scale solar developments in our region. Let’s take a look at the numbers to see what is possible.
Two statewide studies have been conducted in recent years. Both studies project how the solar development market will behave over the coming decades. They examine the best regulations and financial incentives to use to guide the market.
The “Massachusetts 2022 Clean Energy and Climate Plan for 2050,” released in 2022, analyzed multiple pathways to achieve a clean energy future with net-zero carbon emissions. They found that in all cases, tens of thousands of acres of ground-mounted solar will be required to meet the state’s goal.
In a 2023 report “Growing Solar, Protecting Nature,” Mass Audubon and Harvard Forest take a deep dive into this question. Their focus is on finding ways to maximize the use of the built environment (rooftops, parking lots, closed landfills, brownfields, etc.) and minimize impacts on prime agriculture and forest lands. They conclude that substantial financial incentives would be needed to overcome cost barriers for expensive options such as solar canopies over parking lots. Even in their best-case scenario tens of thousands of acres of ground-mounted solar are required.
Statewide studies are useful, but let’s look at the potential for using the built environment in Hampshire County. The statewide target for new solar installations is more than 22,000 megawatts (MW) of power production by 2050. To put our numbers in context, let’s say we need to locate 1,000 MW of this total in Hampshire County. We will ignore financial limitations and just add up the available area for solar and see how it compares with our target.
Let’s start with parking lot solar canopies. These are shed-like structures built over parking lots with solar panels installed on their roofs. UMass has several examples, and the River Valley Coop in Easthampton has an impressive installation. Ever wonder how much power could be generated if all the Hadley mall and big box store parking lots were covered with solar panels? Well, the area of the parking lots is about 100 acres. Applying a typical “solar land use factor” of three acres needed for each MW we can calculate the capacity at about 33 MW. A detailed accounting across Hampshire County of commercial parking lots available for solar might bring this total to perhaps 100 MW. Ok, that’s a start towards the 1000 MW target.
Let’s think about building rooftops. This is a great success story of solar development.
Statewide about 3,000 MW have been installed on residential and commercial buildings, and it is easy to find them on rooftops in our neighborhoods. But a typical residential rooftop installation is only 6 kW (0.006 MW). There are about 46,000 owner-occupied residential units in Hampshire County. If it were possible to have solar installed on their rooftops we would add 278 MW. Impressive, but many of these houses are unsuitable due to excess shade or inappropriate roof slope and orientation.
How can we use closed landfills for solar? They have no shade and have few alternate uses. Nearly every town in the county has a closed landfill. Among the three biggest are the landfills located in Easthampton, Northampton and Amherst. At those three, solar totaling about 7 MW is already installed. Many of the remaining landfills may be suitable for solar siting, but they won’t add much to the county total.
Our tally of possible locations has yielded several hundred MW of solar power, but this
is not close to the 1,000 MW goal. Can we squeeze more solar onto the built environment? We should try. However, it looks nearly impossible to get to 1,000 MW on the built environment alone. We will have to use our fields and forests wisely to provide the space needed to reach our solar goals.
David Ahlfeld is a retired professor of civil and environmental engineering who, when it
comes to energy matters, prefers numbers over adjectives. He lives in Amherst.