Heating and cooling will be tough for Concord to switch to 100% renewable

  • This estimate of sources of fuel for heating in Concord buildings shows the complexity of the situation with thermal energy. Concord Energy & Environment Advisory Committee—Courtesy

Monitor staff
Published: 8/19/2019 9:34:19 AM

As Concord looks at ways to have 100% renewable energy in the entire city, it faces three areas that need to transition: electricity, which will be hard, and transportation, which will be harder. And then there’s the really hard part: Heating and cooling, known in the industry as “thermal energy.”

“The challenge of transitioning to renewable thermal technologies is that the conversion must take place on a building-by-building basis. There is no ‘thermal grid’ equivalent to the electricity grid, meaning that building owners cannot simply plug into a system that is carrying renewable thermal heat,” is how the first draft of the city’s Renewable Energy Goal Strategic Plan puts it.

That 55-page draft, the latest step in the city’s goal of having 100% renewable energy by 2050, went to the City Council two weeks ago and is being parceled out among city departments for consideration. It is full of recommendations, some technical but most regulatory and procedural, and will be the topic of considerable discussion, including public hearings, in the months to come.

For all three of the major areas considered – electricity, transportation and thermal energy – the report recommends two steps to start with: Get good records about how much is being used, and become more efficient because using less makes it easier to transition to renewable sources down the road.

The third major recommendation? Lots of public outreach and communication.

“Education on what homeowners and building owners can do, that’s going to be especially important for thermal,” said Kelsey Sullivan, an attorney with Rath and Young who specializes in renewable energy. She was the lead author of the Thermal Energy chapter of the draft report.

Going backward

Thermal energy is generally acknowledged as the most difficult area to transition to a renewable future because it is so dispersed among locations and among fuels. In Concord, for example, some buildings use natural gas while others use electricity, fuel oil, wood, LP gas and solar thermal, each of which comes from a different provider.

Just figuring out how much of each fuel gets used is hard. The draft report includes a pie showing the fuel source for city buildings gathered through annual surveys done by the Census Bureau, but it only counts the number of buildings, not their actual energy use. By comparison, the electricity chapter of the Strategic Plan shows how much electricity was used in 2018 in all of Concord’s buildings, calculated to nine significant digits.

Only natural gas has good thermal data, because there’s only one provider: Liberty Utility says about 1,400 buildings in the city use 11 million therms of natural gas each year.

Part of the obstacle for renewable thermal is that the city has gone backward. Concord did have a renewable thermal grid until two years ago, when the aging Concord Steam system shut down after running out of money, unable to compete against much cheaper natural gas heating.

For decades its wood-fired plant in the Hugh Gallen Office Part sent steam through underground tunnels to 180 buildings through the downtown as part of a district heating system. Wood-fired district heating is one of the ways often cited for cities to take advantage of renewable energy sources.

Virtually all former Concord Steam customers have switched to individual gas-fired heating and cooling systems, sharply decreasing the city’s renewable-energy footprint.

Many options

A major technological change in recent years that has made renewable thermal more feasible is ground-sourced and air-sourced heat pumps. These condense latent heat either from underground water or from the air and transfer it into buildings, and can be used both as heating systems and as air conditioning.

Air-sourced heat pumps got a bad reputation in New England in the 1990s due to their inability to cope with long winters, but the technology has improved greatly in recent years. They are now said to be a viable option in all but the coldest parts of New England. Because they are powered by electricity they are efficient and can become more environmentally friendly as the electric grid becomes more renewable and cleaner.

“Heat pumps are one of the biggest ideas out there and might have the most potential for the general population converting to renewable there,” said Sullivan.

But this technology is new and few have adopted it yet.

“We got a lot of interest at public meetings from people who want to see demonstration projects and open houses … I think a lot of people are completely unfamiliar with how those look,” she said.

In particular, she said, there is uncertainty about the money side.

“It’s the economics; how cost-effective is it, what’s the payback period? … I think that’s the kind of information people want to know. Is this a long-term financial benefit?” she said.

Another possible source for renewable thermal energy is what is sometimes called renewable natural gas, obtained from organic sources like the city’s sewage treatment plant rather than from fossil fuels.

But no matter the source, with thermal energy even more than other types of energy, Sullivan said, efficiency is key.

“The first step is always conservation. Getting energy efficiency audits, tightening the building envelope … can make a big difference,” she said.

(David Brooks can be reached at 369-3313 or dbrooks@cmonitor.com or on Twitter @GraniteGeek.)

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