The Impact

Air-source vs. Ground-source heat pumps

To: The Impact Readers

🤔 A GoKart that beats Teslas at the drag strip…This concept literally was a joke post after Daniel wrote a piece on a new motor architecture Turntide is commercializing. Well now it’s a real project we’re building an electric GoKart powered by some of the most advanced electric motors coming to market.

Want to get involved?

Reply and let me know!

– Swarnav S Pujari


☀️ Solar Cell innovation can unlock hyper-growth for the solar industry… Leading Edge’s CEO sat down with Daniel Kriozere to share how he plans to help take their new cell architecture get to market after a 10-year lab incubation period and deliver higher power and larger solar panels.

🌱 Startups coming to the rescue of farmers during California’s drought… with water quadrupling from $500/acre to $2,000/acre farmers are losing all of their small margins – in turn driving startups in precision ag to invest heavily into reducing inputs for similar or increased output.

🚖 NYC TLC finally lets Revel enter with 50 EVs… after an arduous battle, Revel gets a small win against the TLC – though it introduces future infrastructure reliability concerns should EV fleets become commonplace in the city,

🥵 Maybe ground source heat pumps aren’t the best choice… We break down how subsidies and temporary incentives may be geared to the wrong technology to drive electrification in homes. Simply put air source heat pumps deliver similar operating costs at a fraction of the up front cost.


The Leading Edge Of Solar Wafers

By: Daniel Kriozere

Leading Edge is revolutionizing the solar industry with their new silicon wafer manufacturing technology. (Image: Leading Edge)
Leading Edge is revolutionizing the solar industry with their new silicon wafer manufacturing technology. (Image: Leading Edge)

Even though the development of solar energy has come down in price and is critical to transitioning to clean energy, how clean are these solar panels? Rick Schwerdtfeger, CEO of Leading Edge, digs into this question from the perspective of the manufacturing process.

What problem are you trying to solve?

We’re trying to solve a couple of problems simultaneously, but the biggest one we’re trying to solve is to do our part to tackle climate change. Leading Edge is doing that by trying to enable a lower cost and better way to make silicon wafers for solar cells.

The second problem we’re trying to solve is the ability to make those solar wafers, cells, and modules in the US. We’ve lost that ability and we’re trying to rekindle that because our technology is advantageous enough that we can make silicon wafers in the US and have a cost advantage over the latest technology in Asia.

Why are you solving this problem?

I’m solving this problem for two reasons. First of all, I’ve had a keen interest in helping commercialize solar energy since I was in high school. My parents put a solar thermal system on our farm back in 1978, and I saw what an amazing job it did heating our old rural farmhouse in Illinois. At that time, nobody was doing that, especially out in the rural midwest.

As a result, when I went to school, I got a bachelor’s degree in physics and got a master’s degree in solar thermal energy. Unfortunately, at that point it was too late to try to work in that industry – it was dying after the Carter tax breaks were wiped out during the Reagan administration. So, I got my PhD in material science, specializing in photovoltaic materials, and then spent part of my early career studying solar energy. However, I left the solar field because there were not yet many jobs in the sector.

The core of what I was doing set me up to solve this problem today. I have been growing crystals, designing furnaces, and developing processes my whole career. When this opportunity came around to be back in the solar industry, using my skills as an entrepreneur, a manager, and as a scientist, it was the perfect alignment for me to now be able to tackle this problem again.

How did you end up joining Leading Edge?

Leading Edge’s technology began more than 12 years ago. Varian started working on this technology before they were bought by Applied Materials. Following that, the scientist that was working on it and an four-degreed MIT PhD engineer got together and spun it out of Applied Materials.

I entered the picture 4 years ago. I actually gave the company an SBIR grant for technology development when I was working at the National Science Foundation. I knew that it was right down my alley. It was a crystal growth, furnace development, and process development project – all the things that I had been doing for literally 30 years.

It was a couple of years later when Leading Edge was hiring a new CEO that I was asked by the board to apply. So, I left a federal government job to jump back into a startup – a world of craziness, challenges of raising money, helping to solve technical problems, hiring people, and all the other challenges associated with being an entrepreneur that I had been through with my previous startup.

What is the core technology of Leading Edge?

The core of the company lies on our ability to make single-crystal wafers horizontally by this kerfless ribbon growth process. We call it the FSM method, the Floating Silicon Method. FSM has never been commercialized anywhere in the world. There have been other vertical ribbon growth technologies commercialized. Pulling horizontal ribbon out of a melt offers a lot of advantages that vertical ribbons don’t. It’s also the first time a ribbon growth technology has successfully made single crystals of silicon wide enough to make modern solar wafers on. That’s the key differentiator for any other kerfless ribbon process – that we can make single crystals.

Fundamentally, we have to be really good at making these ribbons, cutting them into wafers, and doing it fast enough that the costs are low enough that we can beat any other competition. The cost is dependent on the rate at which you pull the ribbon out of the furnace, and if you can double the rate that you pull the ribbons, your cost goes down dramatically. One of our main R&D focuses is to figure out ways to pull these ribbons faster, which will enable us to attract more investors and make it easier to build new plants.

This is a very capital-intensive project because we will have to build a lot of furnaces to do this at scale. By 2030, we’ll need to have roughly 4,000 furnaces. We can ultimately get the cost of the capital equipment down to roughly 50% of what it is today, but it’ll probably take us five years to get there.

What are the benefits of the horizontal ribbon growth strategy versus vertical?

It’s better to talk about the advantages of the horizontal ribbon growth compared to the conventional way, which is a vertical growth process, but it’s not ribbon growth. Instead, it’s big round cylindrical ingot that is grown vertically out of a melt. That’s how all the single crystal silicon wafers in the world today are made. And it’s all done in China.

The advantage Leading Edge offers is that we don’t have saw wafers from big ingots – which turns almost half of the material into sawdust and can’t recycle because it’s too dirty. By having a kerfless process, there’s no sawdust created to make these ribbons because they’re formed at the correct thickness.

There’s only one company that I’m aware of that is trying to do a similar thing to Leading Edge. They are making a small number of wafers at a time, and they’re grown via a gas-phase process resulting in similar savings on kerf reduction and energy savings.

One of the nice things about being in such a high-growth market is that we could both be wildly successful, multi-billion-dollar companies and never have to really compete with each other. The market is so big and growing so fast that we don’t have to try to kill our competitor. We can encourage others to be successful in addition to us so the entire industry can grow and solar can increase its market share over conventional energy sources.

You touched upon this briefly, but how are you thinking about impact?

Reducing kerf waste does two things. It not only saves the raw material because you don’t have to use as much silicon per wafer, which saves cost, but it also saves a huge amount of energy, which can be globally impactful because the amount of energy it took to make that raw material that turned into sawdust by the other method is huge. It’s projected that by 2030, 5% of global CO2 emissions will be from the solar industry, most of which is coming from making the raw material to go into the furnaces. If everyone were to adopt our technology, the maximum impact would be cutting the emissions produced by the solar industry down to 2.5-3%.

What are current and future trends in the space?

The industry is on a trend of larger modules with higher power output. The path to higher output includes larger wafers. Also, innovation is making it possible to cut those wafers into halves or thirds to further increase power outputs by reducing resistive losses.

What that means for Leading Edge is that we need to be able to produce larger wafers over time. As a result, our R&D group is focused on not only pulling ribbons faster but pulling them wider so that we can cut bigger wafers out of them. This will help enable the entire industry to go to higher and higher power modules.


The solar industry is booming, and it is going to keep accelerating – solar is here to stay, and Leading Edge is innovating to improve on energy generation in solar cells. In 2020, 82% of all new power capacity at the utility-scale was renewable. Leading Edge’s technology will only continue to help drive the prices of new solar projects down. 

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Precision Agriculture & Carbon Management To Aid Rising Water Costs

By Jeff Macon

Another drought is crushing California, how are startups helping solve this challenge. (Image: Unsplash)
Another drought is crushing California, how are startups helping solve this challenge. (Image: Unsplash)

With another drought gripping the Western U.S., water costs are rising for the California agricultural industry, which produces over $40B of economic output per year. Water costs for farmers and the ‘ag’ community in California are typically measured in acres per foot. And, these costs have risen from around $500 per acre-foot to over $2,000 per acre-foot for water in some cases. How can farmers offset this significant cost increase when their margins are razor-thin?

Startups have been selling solutions to farmers in California to help them reduce their inputs including water and fertilizers while maintaining or even improving crop yields. Startups in this space are often referred to as precision ag ventures. Also, carbon management plays have started to garner attention as a number of countries around the world now pay for carbon to be sequestered, typically in the ground.

Can precision ag and carbon management startups help California farmers continue to provide food to our markets while maintaining viable business models? If droughts in the Western U.S. continue increasing the cost of water for ag, they may have to.

Here are some recent ag-tech startups I’ve come across with precision ag or carbon management plays:

Precision agricultural startups:

We’re trying to solve a couple of problems simultaneously, but the biggest one we’re trying to solve is to do our part to tackle climate change. Leading Edge is doing that by trying to enable a lower cost and better way to make silicon wafers for solar cells.

The second problem we’re trying to solve is the ability to make those solar wafers, cells, and modules in the US. We’ve lost that ability and we’re trying to rekindle that because our technology is advantageous enough that we can make silicon wafers in the US and have a cost advantage over the latest technology in Asia.

Why are you solving this problem?

Reservoir, based in Georgia, helps farmers automate their legacy irrigation practices to minimize water use while maintaining crop yields by deploying wireless sensors with exceptional range. Perhaps Reservoir would be a good licensing or merger-and-acquisition candidate for a larger competitor.

Kairospace Technologies, based in Argentina and California, provides irrigation equipment for crops and livestock including pre-treatment of water in washing food products, supplemental aeration for wastewater treatment, advanced oxidation processes in mining and other highly polluting industries. If Kairospace successfully integrates proven technologies, they could help not only agriculture manage water, but mining operations, too.

Verdi, based in Canada, is working to ‘climate proof’ farming by bringing the precision of indoor farming to outdoor agriculture. They are developing AI-powered networks on farms to customize nutrition for sections of individual crop rows, and eventually for every single plant.

Carbon management startups:

Nurture Growth Bio, based in Canada, reduces food waste, the third-largest emitter of GHG by upcycling food waste to eco-friendly microbial fertilizer. Beneficial microbes from food waste are transformed into a biofertilizer to build healthy soils and promote plant growth.

Lemna, based in Arizona, uses a duckweed plant to remediate livestock wastewater which reduces nutrient concentrations from getting into groundwater and surface water. If Lemna proves the benefits of using duckweed to treat water at dairies and hog farms, we’ll have quite a bit more water to go around.

Boomitra, based in California, deploys software to help farmers and ranchers measure soil moisture, nutrients, and soil carbon so they can minimize inputs, maximize outputs, and sell carbon credits. Boomitra’s recent $4M investment round from Yara International and Chevron Technology Ventures suggests they are onto something in terms of helping farmers earn carbon sequestration credits.


Climate tech startups have always had to navigate multiple ‘valleys of death’ to create successful business models. With all the attention and momentum there currently is around the world to manage carbon as well as water, these startups, and those similar to them should find it a lot easier to get the funding, talent, customers, and partners they need. Necessity, perhaps.


The Future Of Mobility Post Revel’s Approval In NYC

By Daniel Kriozere

Revel gets approval for EV only rideshare service (Image: Revel)
Revel gets approval for EV only rideshare service (Image: Revel)

Revel is a transportation company that’s electrifying cities through charging infrastructure and shared electric vehicle fleets. Starting on August 2nd, Revel will be launching an app-based car service for 50 Tesla Model Y SUVs in New York.

How does New York feel about the addition of more vehicles in the city?

Taxi & Limousine Commission (TLC) spokesman Allan Fromberg mentioned that “There are approximately 120,000 TLC licensed vehicles in New York City, taxi and for-hire vehicles combined, and the TLC continues to encourage as many of those vehicles to convert to battery electric vehicles as possible.”

This led to the initial “reason” for the TLC to close off a loophole that would allow Revel to enter into the NYC ridesharing market and cause some political discourse prior to this recent shift opening the city back up to them.

Meanwhile electrification is a step forward in the right direction to reduce emissions, what does the increase in vehicles in New York City entail? Granted, Revel is only starting with 50 of them, there will be more to come. The real question is what does the phase out plan look like for existing internal combustion engine vehicles?

It is just as important, if not more important, to acknowledge that the current 120,000 TLC vehicles today need to be replaced by electric vehicles. New York City might look towards California’s recent executive order ban on the sale of new gasoline-powered passenger cars and trucks, which starts in 2035. A policy like this will incentivize fleet owners to consider electrification much sooner. This leads to my second question.

What does this mean for New York City?

New York City is not ready for the demand of the increase in electric vehicles. As a result, Revel CEO Frank Reig hopes to build more charging stations. Even if more charging stations are built, the grid does not have the capacity. As a result, Revel is working with Con-Edison to identify locations for new charging stations and electricity substations.

What does this mean for the future of mobility?

New York City is a stellar example of a city reliant on public transportation and ridesharing. If New York City is facing challenges to electrify, what does that mean for other big cities?

Situations like this show that for as essential electrification is, we cannot rely solely on electrification for transportation. This is where policy can be a great motivator to nudge businesses and markets to adapt quickly. If there is no policy, businesses and cities would be much slower to transition away from fossil fuels. Policy can also accelerate investment and commercialization of other technologies, from biofuels to solid oxide fuel cells.


The Problem With Ground Source Heat Pumps

By Nate "The House Whisperer" Adams

The argument for air source heat pumps over ground source heat pumps. (Image: Green Square)
The argument for air source heat pumps over ground source heat pumps. (Image: Green Square)

I don’t like ground source heat pumps.

This position typically takes people by surprise. To be clear, I’m talking about single-family homes in particular. Let’s explore the details.

First off, definitions. A heat pump moves heat from one place to another. Your refrigerator is a heat pump. It takes heat out of the cold air inside and pushes it into your kitchen. The source is the cold air inside your fridge, the place it rejects the heat is into your house.

An air conditioner is technically a heat pump, it takes heat from inside your house and ejects it into the hot outdoors through something called the refrigeration cycle.

An “air source heat pump” in US parlance is an air conditioner that can heat as well as cool. In winter it takes heat out of the cold outdoor air and puts it inside your house. It’s EXACTLY what your fridge does.

ground source (aka geothermal) heat pump takes heat from the earth through a long pipe loop that is either horizontally about 6 feet down in a large field like a septic field, or vertically several hundred feet down that takes up very little space in your yard.

The Question

Joel Zook in the Electrify Everything Facebook Group asked me my position on ground source for his older home in a very cold climate (Climate Zone 6, Wisconsin and Minnesota are the only states with substantial population in those zones.)

My Answer

That would be a place to consider them. My issue is that even after the tax credit they are typically $10k-20k more. That $10k-20k can usually make a good sized dent in shell work.

A particular client of mine spent ~$35k on a ground source heat pump, which is about $25K after the tax credit. He had very high energy bills and an uncomfortable house.

He could have forgone the tax credit, spent $5,000 more out of pocket, got an air source heat pump and an insulation and air sealing package, then had very low bills and a comfortable house.

Instead, he’s using 21,000 kwh/year (total annual usage, not just HVAC).

Our other clients with similar sized homes with air source heat pumps are using 12,000 to 15,000 kWh year, and report that they are amazingly comfortable.

His house is very uncomfortable AND uses more energy AND it cost more to do (both him and the government) AND costs more to run. This is pretty typical in retrofits, I’ve had several other clients in the same boat.

Remember, for $5K more he could have had a very comfy home that uses less and costs less to run. I hate talking about payback because it’s the path to hell, but it would have saved him $700-1000/year in operating costs with an air source and insulation/air sealing path.

Ground source heat pumps are typically poor resource allocation. Money is limited, spend it wisely.

The exceptions are Climate Zone 6 and up, particularly in larger homes that are tough to reduce load on. The big risk is undersizing the loops or poor soil quality. It’s distinctly possible to remove more heat in winter than gets replaced in summer and end up running on resistance a big chunk of the winter. Design and install are very finicky on ground source and there are very few contractors in most markets that can service them.

Electrification for you is likely to cost $20-30K extra with geo than it is with a hybrid furnace and air source heat pump. I question if that’s worth it for what is likely a few hundred therms per year. I’d rather you use that money towards an EV or other high impact fossil reduction (even donating to causes.) 

Market Distortions

Some will talk about Dandelion now. NY is THROWING money at heat pumps, plus there is a 30% tax credit. Take those away and the economics of ground source are positively laughable.

The rule of thumb in policy is that beyond 1% market penetration, incentives get too expensive to continue. So we incentivize a few systems, build a small contractor network, then pull the rug out from underneath them.

I watched this happen with one geo company local to me in Cleveland. I drove by their shops over the years, they had a little one, got a really big one when the tax credit was on, then downsized again as the ground source tax credit came and went. I have several friends who got into the business with the tax credit, then got back out when it went away.

The same thing happens with efficiency/rebate programs. Robert Brierley watched 30 competitors die over the last few years when the efficiency program in Portland shut down. This same cycle happens with every program if you look closely. It’s one of the big reasons we are so anti-program.

If a product or program isn’t 100% sustainable without any incentives, it should die. Period.

Why? Because sooner or later the programs will die.

In fact, most programs make it harder for the 100% market based path, they subtly or blatantly shift the sales process or product selection, which kills closing ratios and job sizes.

This ends up messing up markets and preventing them from growing.

Because ground source requires drilling a loop for $8k-20K AND the equipment is the same price or more expensive than air source, it will always need help to be cost competitive in the market. Therefore it will die when programs are removed, which will happen at some point.

PLUS, even with that 30%, they still cost more and create the client situation I mentioned above, which I’ve seen multiple times.

If we want electrification to scale, products and business models MUST stand on their own.

This is a critical point. If we pull for anything that can’t survive without help, we are destroying our future chances at decarbonization.

Technical Improvements

One other key point: air source heat pumps have improved DRAMATICALLY over the last decade.

Ground source often made sense vs crappy single stage air source heat pumps.

Now inverters have changed the game. Ground source remains marginally less expensive to operate, but air source heat pumps reduce upfront cost as well as cost roughly the same to operate. It’s a few hundred per year difference where it could have been as much as a few thousand 10 years ago.

Ground Source Favors the Wealthy

There is a lot of discussion about equity right now. Ground source heat pumps don’t fare well here. First, they are primarily for the wealthy because:
a) they pay enough taxes to use the tax credits that come out of these projects and
b) they are best applied to larger homes with high heat loads.
Are we sure we want to use large amounts of government money to subsidize a market that really shouldn’t need subsidies?

For example, let’s look at the project aforementioned. It generated a ~$10,000 tax credit. With the 3H (Hybrid Heat Homes) proposal, that same amount would buy 20 heat pumps that would reduce gas usage 30-50% for those homes, and they would be predominantly middle class homes. So that $10K can decarbonize one home or the equivalent of 7-10 homes. What is the better allocation of capital and fairness? This is a question that could use more discussion.

Outlook - Do the Math


In most single family electrification retrofits, the first thing to do is insulation and air sealing. Especially in cold climates. That is often the best place to aim your money (leaving aside the fact that you are VERY unlikely to get it back at resale, another major market distortion.)

If we want to decarbonize, don’t we want to do it in the most cost efficient way that provides a great experience?

If we want to see electrification move quickly, it needs to be done in the most effective and efficient way possible that also creates huge value. That way the majority of the market will do it.

Editors: Swarnav S Pujari, Daniel Kriozere Writers: Nate Adams

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