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DALL·E created image of a warm and comfortable home interior with a family in the style of impressionism
DALL·E created image of a warm and comfortable home interior with a family in the style of impressionism


The Magic of Heat Pumps: Transforming Homes & Combating Climate Change

Harvest Thermal is a company focused on electrifying home heating and hot water systems with its thermal storage heat pump technology. The system reduces homeowners’ energy costs and carbon emissions by shifting heat production to off-peak hours and optimizing energy use through stratified thermal storage and data-driven controls.

Harvest Thermal is a heat pump company that aims to decarbonize heat for homes and small buildings while also saving homeowners money through thermal storage. I had the opportunity to chat with Dr. Jane Melia, founder and CEO, late in 2022 for CleanTechnica‘s CleanTech Talk.

You can find our CleanTech Talk podcast episodes on AnchorApple Podcasts / iTunesBreakerGoogle PodcastsOvercastPocketPodbeanRadio PublicSoundCloudSpotify, or Stitcher. If you prefer a Spotify embed over a SoundCloud embed, you can find that toward the bottom of this article.

This article summarizes the second half of our conversation, but with a twist. Normally, I listen to the podcast, make notes and turn them into an article. This time, I downloaded the audio file, put it through an automatic free web transcription service, then had ChatGPT summarize it for a popular technology audience.

Harvest Thermal is focusing on the residential market, specifically small multifamily and single family homes. These homes often use fossil fuel combustion, such as gas or oil, to heat their homes, and Harvest Thermal is targeting this market because there are few good options available.

The company has initially deployed its heat pumps in the California Bay Area and Santa Barbara, and plans to expand to Portland, Oregon and the West Coast in 2023. The technology can also be used in other climates, but it is important to size the heat pump and storage tank to meet the needs of the specific home.

Harvest Thermal’s thermal storage system allows it to shift heat production to off-peak hours when energy is cheaper, reducing the impact on the electric grid and the cost to homeowners. Most homes in the San Francisco Bay Area have forced air systems for heating and cooling, with a smaller number using radiant heat. Harvest Thermal’s heat pumps can work with either system.

Water is a particularly efficient medium for thermal storage because it has a high energy density and does not change volume as it absorbs or releases heat. The fluidity of water also allows it to be used as a variable capacity battery in systems like Harvest Thermal’s heat pumps.

Stratified thermal storage is a technique used in heating and cooling systems to optimize the use of energy. In stratified thermal storage, the temperature of the storage medium (such as water in a tank) is varied over the height or volume of the tank. This allows the system to heat or cool only the amount of the medium needed for the current demand, rather than heating or cooling the entire tank.

For example, in a heat pump system using stratified thermal storage, the top layer of water in the tank may be heated to a high temperature to meet the current demand for hot water. The bottom layer of the water in the tank may be cooler. This stratified temperature gradient allows the system to use less energy overall, because it is only heating the amount of water needed for the current demand. The stratification can be maintained through the use of flow meters, temperature sensors, and other controls to continuously calibrate the system and understand the state of the storage tank.

In the fall and spring, more of the tank is heated to meet the additional heating needs of the home. In the winter, the whole tank may be loaded up twice in a 24 hour period on the coldest days. This variable capacity system allows for greater efficiency and cost savings for homeowners.

In addition to optimizing for cost and emissions, Harvest Thermal also places a strong emphasis on comfort. It uses data from the thermal storage tank and heat pump to fine-tune the performance of the system and ensure that it is meeting the needs of the household. The system also has visibility into hot water usage, allowing it to alert homeowners to unexpected changes and potential problems. Overall, the stratified thermal storage and data-driven approach of Harvest Thermal’s solution enables it to optimize energy use and provide a comfortable experience for homeowners.

One example of the benefits of the Harvest Thermal system is the ability to identify unusual patterns in energy use. For example, in one instance, the system alerted the homeowners that they were using hot water at 2:00am, 3:00am, and 4:00am. Upon investigation, it was discovered that there was a hot water leak in an auxiliary unit on the property. This level of visibility and the ability to quickly react to unusual usage patterns can help identify and solve issues before they become more significant problems.

Thermal storage can help optimize energy use by allowing heat pumps to run during times when there is excess renewable energy available, rather than just during times of peak demand. This can help smooth out the demand on the grid and make it easier for utilities to manage. In addition, by using thermal storage, heat pumps can be more efficient and cost effective for homeowners, as they can run at a lower temperature gradient and fill up the thermal battery during times of lower electricity prices. This can help reduce the overall cost of heating homes and buildings, as well as reduce emissions from the grid. Finally, by using thermal storage, heat pumps can provide a more consistent and reliable source of heat for homes and buildings, helping to improve comfort for users.

Harvest Thermal has trained 22 contractors in the San Francisco Bay Area to install their systems, and they have a waitlist of hundreds of homes. The company sees a growing number of contractors who want to be part of the solution to climate change and who see the growing market for heat pumps and electrification as an opportunity. Harvest Thermal plans to grow its business in the places where it makes the most sense for homeowners and where it makes economic sense.

In addition to working on its own product, Harvest Thermal has also announced a partnership with BlocPower, a company that specializes in bringing clean energy solutions to underserved communities. The partnership will allow Harvest Thermal to expand its reach and bring its clean heating solution to more people in need. Overall, the company sees a strong tailwind for their business as there is increasing awareness and concern about climate change, a desire to reduce dependence on foreign sources of gas, and incentives and support from governments and utilities for clean energy solutions.

As always, I asked Dr. Melia for her closing thoughts to the broad CleanTechnica audience.

“Climate change is the most global of issues. Although some of us have more responsibility in causing it than others, and I’m probably one of the guilty parties, being a consumer from a highly developed country. But we are all in it together and we all need to tackle it together.

It’s a global problem, but there’s nothing more local than our homes and our communities, and every home has to be able to transition from often fossil fuel heating and fossil fuel hot water to a cleaner way of doing it. Heat pumps are magic. Heat pumps are a really good way to do it.

And I think there are ways that we can take these Gen One heat pumps and make them to Gen Two heat pumps, which are going to be even better for the planet. And I hope that this type of solution that we’re spearheading here in California, in the US. I think there’s space for it all over the world. I think this type of thing is going to allow electrification to take place at scale in millions and millions of homes, not just in the US. But in Europe, in Australia, in Asia, and all over the world.”

A few notes on the experience:

The first is that, sadly, ChatGPT wouldn’t accept the entire transcript, so I had to put it in a chunk at a time and assemble it — but that really wasn’t onerous. Second, it was easy to ask it to expand on something, like the stratification summary. Third, it quickly generated five alternative catchy headlines, and a two-sentence summary for the article. (It will also generate clickbait versions of headlines too, something I tested on a different article but chose not to use.) Fourth, it was easy to get it to fix its errors, like thinking that Dr. Melia’s firm was called EchoGen and spelling BlocPower as BlockPower, just by asking it to. Fourth, the decorative image was generated by ChatGPT’s sibling product DALL-E when asked for “a warm and comfortable home interior with a family in the style of impressionism.”

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Written By

is a member of the Advisory Boards of electric aviation startup FLIMAX, Chief Strategist at TFIE Strategy and co-founder of distnc technologies. He spends his time projecting scenarios for decarbonization 40-80 years into the future, and assisting executives, Boards and investors to pick wisely today. Whether it's refueling aviation, grid storage, vehicle-to-grid, or hydrogen demand, his work is based on fundamentals of physics, economics and human nature, and informed by the decarbonization requirements and innovations of multiple domains. His leadership positions in North America, Asia and Latin America enhanced his global point of view. He publishes regularly in multiple outlets on innovation, business, technology and policy. He is available for Board, strategy advisor and speaking engagements.


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