The secret to decarbonising buildings lies under your feet

Crews drill a borehole to install networked geothermal, which heats and cools nearby homes using the ground as a battery. Eversource

From Grist

Along with earthworms, rocks, and the occasional skeleton, there’s a massive battery right under your feet. Unlike a flammable lithium ion battery, though, this one is perfectly stable, free to use, and ripe for sustainable exploitation: the Earth itself.

While temperatures aboveground fluctuate throughout the year, the ground stays a stable temperature, meaning it’s humming with geothermal energy that engineers can exploit. “Every building sits on a thermal asset,” said Cameron Best, director of business development at Brightcore Energy in New York, which deploys geothermal systems. “I really don’t think there’s any more efficient or better way to heat and cool our homes.”

At the start of June, Eversource Energy commissioned the United States’ first networked geothermal neighborhood operated by a utility, in Framingham, Massachusetts. Pipes run down boreholes 600 to 700 feet [200 metres] deep, where the temperature of the rock is consistently 55 degrees Fahrenheit [13 Celsius]. A mixture of water and propylene glycol (a food additive that works here as an antifreeze) pumps through the piping, absorbing that geothermal energy, then flows to 31 residential and five commercial buildings, where fully electric heat pumps use the liquid to either heat or cool a space. If deployed across the country, these geothermal systems could go a long way in helping decarbonize buildings, which are responsible for about a third of total greenhouse gas emissions in the U.S.

Once a system is in place, buildings can draw heat from water pumped from below their foundations, instead of burning natural gas piped in from afar. Utilities use the same equipment to deploy networked geothermal as they do for gas lines, and even the same kind of pipes — they’re just circulating fluid instead of gas. The networks don’t need special geology to operate, so they can be set up pretty much anywhere. The project in Framingham, then, could be the start of something big.

In Massachusetts, commercial buildings tend to be more cooling-heavy, meaning that they cool more than heat over the course of a year, whereas residential homes tend to be more heating-heavy. Lots of different structures, with different heating and cooling needs, share one loop of piping in a geothermal network. “When you combine them onto the same loop, you keep the ground temperature stable,” said Eric Bosworth, manager of clean technologies at Eversource Energy. “You’re not putting energy in or out of the ground when you add all of the loads up.”

To scale up, a geothermal loop like Framingham’s might connect to an adjacent neighborhood, and that one to another. “In the end, what we would like is if the gas utilities become thermal utilities,” said Audrey Schulman, executive director of the nonprofit climate-solutions incubator HEETlabs (a spinoff of the climate nonprofit HEET, which began pitching the idea to Eversource and other utilities in 2017). “Each individual, shared loop can be interconnected, like Lego blocks, to grow bigger and bigger.”

That goal may not be far off as utilities face increasing regulatory pressure to phase out gas. So Eversource Energy and two dozen other utilities, representing 47 percent of the country’s natural gas customers, have joined into an information-sharing coalition called the Utility Networked Geothermal Collaborative. “We’ve made a point to think about: Are we really a gas company, or are we a thermal energy delivery company?” said Holly Braun, business development and innovation manager at the Oregon utility NW Natural, which co-founded the coalition.

These geothermal systems hinge on the humble heat pump. For most homes, an “air-source” heat pump is currently the best option: Using an outdoor unit, it extracts warmth from even chilly winter air and pumps it inside. It then reverses in the summer to act like an air conditioner.

A heat pump in a geothermal system works the same way, only instead of extracting heat from air, the appliance extracts it from the water that’s been coursing underground. In the summer, the heat pump cools a space by injecting indoor heat into the water, which is then pumped back into the Earth. That helps warm up the ground, recharging the subterranean battery so there’s plenty of energy to extract in the winter.

A networked geothermal system is extremely efficient. It scores a “coefficient of performance,” or COP, of 6, meaning for every one unit of energy going in, you get six units of heat out. By contrast, gas furnaces have a COP of less than 1.

These heat pumps are exploiting water moving through rock that’s consistently 55 degrees [F; 13 degrees C]. An air-source heat pump in the same neighborhood might have to run when it’s 10 degrees [F; -12 degrees C] out, meaning it’ll have to work harder to provide the same amount of heat. Accordingly, its COP of 2 or 3 would still far outpace a gas furnace, but not approach geothermal’s COP of 6. “That means you have a higher efficiency with a ground-source system, which, of course, helps then with running costs,” said Jan Rosenow, who studies heat pumps at the Regulatory Assistance Project, a global energy NGO.

That kind of efficiency will be critical if the U.S. is going to wean itself off fossil fuels. The more gas furnaces people replace with electric heat pumps, the more demand on the electrical grid. But the more efficient that engineers can make heating and cooling systems, the less capacity utilities will have to add to the grid. “Ground-source heat pumps, and particularly those community networked shallow geothermal, take the lowest electricity draw on that coldest day in winter,” said Tamsin Lishman, CEO of Kensa Group, which is pioneering networked geothermal in the United Kingdom. “It supports a substantial saving in the upgrade needed in the grid.”

But if a utility has perfectly good infrastructure already in the ground to deliver gas, and it’s making good money doing so, why would it invest in a new kind of geothermal infrastructure? The reality is that a lot of that gas infrastructure isn’t particularly good, and is downright dangerous if it’s leaking an explosive gas. A utility might use networked geothermal to just swap in water for gas. “If you’re in a situation where you’re going to need to upgrade your pipe anyway, or replace it, you maybe think about: Do I replace it instead with a pipe that doesn’t require fuel, and it’s naturally replenishing energy from the ground?” Braun said.

At the same time, utilities are under mounting pressure to phase out natural gas: Last year, New York became the first state to ban it in most new buildings. Utilities are also staring at mandates in states like California, Vermont, and Colorado to slash their overall carbon emissions, and they can’t do that if they keep delivering the same amount of natural gas. “If you’re in a jurisdiction that says ‘no new gas,’ well, you don’t put in new gas,” Braun said. “You’ve got to have something else, or you just keep shrinking your business.”

For new housing developments in particular — especially where recent ordinances have limited the amount of new buildings that can be connected to gas — they can drill the boreholes and lay the piping for buildings, and the homes will be ready to go fully electric. “We could lose those customers — we could just take ourselves out of the game — or we could present them with a new, decarbonized option that utilizes our existing strengths,” said Morgan Hood, manager of innovative products and services at Vermont Gas Systems, which co-founded the Utility Networked Geothermal Collaborative. “That’s what geothermal does.”

Though networked geothermal is vastly more efficient than burning gas in a furnace, it’s still unclear how it would impact a customer’s energy bill. Because utilities are still experimenting with these systems, they haven’t settled on a rate structure. One option may be a flat monthly rate to tap into the geothermal network, depending on how much water a given structure needs to provide adequate heating and cooling. It’s a relatively new technology, so the costs to install are still high: Eversource says its budget for the Framingham project was around $18 million for those 36 residential and commercial buildings. But as with any technology, costs will come down as the technique matures.

If the United States is going to properly decarbonize, the home of tomorrow could ditch natural gas and instead use a heat pump to tap into the air or the earth itself as a natural battery. The energy’s there — it’s always been there — now it’s just a matter of realizing its full potential.

Seems expensive ($500,000 per building!), though, as the article says, costs will fall.  But they'd have to fall a lot to make this competitive.  An air-source heat pump might still end up being a lot cheaper, even though it is less efficient.  However, perhaps they don't need to drill down 700 feet.  Perhaps, going down only 100 feet (30 metres) may still work, even though there would be fluctuations between summer and winter temperatures instead of a steady 13 degrees C deeper down.

Super-cooling nanofibre inspired by ants

‘PhysicsWorld: Cool’ Saharan ants’ silver hairs cause total internal reflection

From BusinessWire

The summer of 2023 was by far the hottest in history. People were seeking solace in air-conditioned spaces or donning cooling attire. Here’s some food for thought: Can buildings also be outfitted with similar cooling solutions?

Led by Professor Dehui Wan from the Institute of Biomedical Engineering at National Tsing Hua University (NTHU) in Taiwan, a research team drew inspiration from the silver ants inhabiting the Sahara Desert and created a biomimetic material called "super-cooling nanofiber."

Covering roofs with this thin, pliable, and durable fiber membrane, which is resistant to UV rays and acid rain, is like adorning buildings with cooling attire. This innovation can lead to a reduction of over 12˚C in indoor temperatures, resulting in significant savings in electricity costs. Furthermore, it aligns with the broader goals of energy efficiency, carbon reduction, and ultimately, the protection of our planet.

Professor Wan pointed out that Saharan silver ants manage to thrive in scorching temperatures of up to 70˚C primarily because of their triangular prism-like hairs. These hairs reflect a significant portion of the sunlight that hits them. Most of the absorbed energy from visible light is converted to longer wavelength infrared light, which is then emitted through the hairs, leading to an efficient cooling effect.

Taking cues from the hairs of these desert-dwelling ants, the research team embarked on a comprehensive exploration of diverse materials, configurations, dimensions, and hues. Using advanced optical engineering techniques, they employed ceramic materials to create white fibers measuring just a few hundred nanometers in diameter. These fibers possess the ability to reflect 97% of sunlight, resulting in a substantial cooling effect.

In the blistering sun, Professor Wan led his students as they conducted experiments on the roofs of campus buildings. They applied the super-cooling nanofiber membrane to the roofs of small-scale houses and used an infrared thermal camera to measure the temperature. This resulted in a notable decrease from 50˚C to 29˚C. Likewise, temperatures often rose to 60˚C inside a model car during the hot summer days. Yet, after applying the super-cooling nanofiber membrane, the temperature decreased by 17˚C.

The research team found that this innovative ceramic nanofiber doesn't just reflect sunlight; it also converts absorbed heat into infrared radiation, which passes through the atmospheric layer known as the "atmospheric window" and dissipates into the cold vastness of outer space, rather than being retained at the Earth's surface or in the atmosphere. This development holds promise for mitigating the greenhouse effect, providing a ray of hope in the battle against global warming.

The research project, led by NTHU in collaboration with National Taiwan University and National Yang Ming Chiao Tung University, achieved international recognition when it was published in the prestigious journal Nano Today in February 2023. The team is currently in the process of applying for twelve domestic and international patents for the super-cooling materials.

If we can cool houses using a nano-fibre cover, we'll be able to use less electricity for air conditioning.  Makes sense. 

Searing China heatwave leads to record electricity demand

From Reuters

Power consumption surged in large Chinese provinces north of the Yangtze river amid warmer-than-normal weather, with regions like Henan, China's third-most populous province, challenged by record electricity demand.

The maximum power demand load in Henan, which has a population of nearly 100 million people, set a new record of 65.34 million kilowatts on Sunday, state television reported on Monday.

While the provincial grid was able to cope with the heavy demand, electricity supply in Henan is expected to be relatively difficult this summer, according to the report, with the maximum load seen rising further to nearly 75 million kilowatts.

In contrast to the heaviest rainfall in 60 years in southern China, Henan and nearby Shandong and parts of Hebei have battled with scorching heatwaves and drought-like conditions this month. read more

Temperatures in Henan's capital Zhengzhou, where major Taiwanese Apple supplier Foxconn (2317.TW) has a production hub, have reached 40 degrees Celsius (104 degrees Fahrenheit) in recent days.

As temperatures climb, demand for power rises as homes and businesses crank up air-conditioning, peaking typically around the end of July and beginning of August in China.

Prolonged periods of high temperatures could force China to limit, stagger or ration power consumption of industrial users during peak periods.

The high temperatures will persist through Tuesday, with Henan, Hebei and Shandong still the core areas of the warm weather, China's meteorological administration said.

"For this region, it is rare to see such persistence and intensity in high temperatures at this time in June," it said.

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Electricity pylon and powers lines are seen in Nanyang, Henan province, China October 13, 2021. REUTERS/Aly Song

Efficiency improvement essential for coal phase-out in China

There is no doubt in my mind that China is very concerned about global heating.  She is by far the largest investor in wind and solar farms in the world, and she has an aggressive EV roll-out plan.  Shet knows that she will suffer as much as any country from global heating, and that she is responsible by herself for 27% of global emissions.  The country's emissions controls are designed to reduce emissions relative to GDP/total electricity demand which means that because GDP/electricity demand is growing so rapidly, total emissions could still rise even if relative emissions fall fast.  '

So it is good news that China uses electricity much less efficiently than other countries.  Improvements in efficiency, combined with the roll-out of renewables and EVs, could stabilise China's emissions or even cut them.

 From EMBER

China – the world’s largest producer and consumer of coal power – has recently promised to ‘strictly limit’ the growth of coal consumption in the next five years (2021-2025) and to phase it down thereafter, as part of its efforts to attain carbon neutrality before 2060. In this context, the future trajectory of coal power in China has become clear: coal generation will peak before 2025 and all unabated coal generation will fall to zero before 2060. Now, the question is how to turn this trajectory into reality. 

Electricity efficiency could be a crucial aspect of the answer to this question. With enormous opportunities for efficiency improvements, it should be put at the forefront for policy making in China, because this would help redress excessive growth of electricity demand, and hence make the phase-out of coal generation easier.

Between 2010 and 2020, China’s electricity demand grew by an average of 8.1% or about 340 TWh per annum – equivalent to the electricity demand across the United Kingdom in 2020. Although renewable generation also experienced exceptional growth over the same time period, it has not been able to, on its own, satisfy the incremental electricity demand. As a consequence, more electricity has also been produced from coal and other fossil fuels in order to maintain the overall sufficiency of electricity supply.

 

It is very likely that the current trend of fast-growing electricity demand will continue in the years to come, mainly driven by rising population and prosperity, as well as the need to decarbonise some of the hard-to-abate sectors (i.e., steel, cement, and transport) through electrification. This demand growth may exceed the speed at which ‘clean’ electricity technologies can be deployed, making the phase-out of coal generation difficult.  

The industry sector is the largest electricity consumer in China, accounting for almost 70% of electricity consumed in 2018. The electricity intensities of various industries in the sector are in general higher than those of the major industrialised countries, though to varying degrees. The difference is likely due to the use of less efficient production technologies, suggesting large potential for electricity savings if more advanced technologies can be adopted. 

The services sector is another major electricity consumer in China, responsible for about 15% of electricity consumption in 2018. It is also one of China’s fastest growing electricity consumers, with annual consumption rising at an average of 16% over the period 2010-2018, from 448 TWh in 2010, to 1,023 TWh in 2018. This compares to 7.4% for the industry sector, 10.5% for the construction sector, and 12.0% for the household sector. The electricity intensity of the services sector in China has exhibited  an upwards trend over the past few years, reaching 0.20 kWh per dollar of sectoral value added in 2018 – more than twice the world average. China’s high electricity intensity of the services sector suggests large potential for improvement.

There also exists significant scope for efficiency improvement in China’s household sector. Consider domestic air conditioners – the main electrical appliance in the household sector – for example. The average annual performance factor of variable speed mini-split air conditioners sold in China over the period 2015-2017 was 7-20% lower than the most efficient units available in the market and 50-60% lower than the best practice units. This means that large amounts of electricity can be saved if more stringent standards could be introduced on the efficiency of air conditioners.

China’s huge potential for electricity efficiency improvements, if realised, could help redress its excessive growth of electricity demand as the economy continues to grow. This, together with an inexorable march of renewable energy, is very likely to expedite the process of squeezing coal out of the generation-mix. Policymakers should therefore put more emphasis on tapping into the country’s potential for electricity efficiency improvement as they draft the 14th energy five-year plan – the first comprehensive policy guidance for steering China’s journey to carbon neutrality.  

Air conditioning feedback

Air conditioning in Mumbai. Source: The Age

From The Age:

The vast majority of Americans and many Australians have air conditioning, but in Germany almost nobody does. At least not yet.

So when temperatures in Berlin rose to an uncomfortable 37 Celsius this week – a record for the month of June – I was uncommonly delighted to go to the Bloomberg office, where it's artificially and blissfully cool.

By letting people in overheated climates concentrate on their work and get a good night's sleep, air conditioning has played a big part in driving global prosperity and happiness over the past few decades – and that revolution has still barely begun.

About half of Chinese households have this modern tool, but of the 1.6 billion people living in India and Indonesia, only 88 million have access to air conditioning at home, Bloomberg New Energy Finance noted in a recent report.

For many, relief is in sight. Because of the combination of population growth, rising incomes, falling equipment prices and urbanisation, the number of air-conditioning units installed globally is set to jump from about 1.6 billion today to 5.6 billion by the middle of the century, according to the International Energy Agency.

There's just one glaring problem: What will all this extra demand for electricity do to the climate?

Carbon dioxide emissions rose another 2 per cent in 2018, the fastest pace in seven years. That increase was alarming in its own right, given what we know about the unfolding climate emergency.

But the proximate cause was especially troubling: Extreme weather led to more demand for air conditioning and heating in 2018, BP explained in its annual review of energy sector.

It's not too hard to imagine a vicious cycle in which more hot weather begets ever more demand for air conditioning and thus even more need for power. That in turn means more emissions and even hotter temperatures.

That negative feedback loop exists at a local level too. Air-conditioning units funnel heat outside, exacerbating the so-called "urban heat island" effect, which makes cities warmer than the countryside.

BNEF expects electricity demand from residential and commercial air conditioning to increase by more than 140 per cent by 2050 – an increase that's comparable to adding the European Union's entire electricity consumption. Air conditioning will represent 12.7 per cent of electricity demand by the middle of the century, compared to almost 9 per cent now, it thinks.

Thankfully, much of that extra demand will be met by solar power (the need for cooling is highest during daylight hours). But because temperatures don't always return to comfortable levels when the sun goes down, there's a danger some will be supplied by fossil power.

Buildings have long been a blind spot in climate discussions even though they account for about one-fifth of global energy consumption. The inefficiency of air-conditioning systems or badly designed homes and offices simply aren't as eye-catching as electric cars and making people feel ashamed about flying.

There was a big step forward in January when the Kigali Amendment to the Montreal Protocol came into force. Though not well known, its aim is to phase out the use of potent greenhouse gases called hydrofluorocarbons, which are used widely in air conditioning systems. Unless substituted, these alone could cause 0.4C of additional warming by the end of the century.

Yet true to form, President Donald Trump's administration hasn't yet submitted Kigali to the Senate for ratification, even though American manufacturers would benefit from demand for the new technologies that it would spawn.

Trump knows all about the importance of good air con. He spends much of his time at his Palm Beach country club, a place that couldn't exist without it.

So he'd do well to remember this: You can air condition the clubhouse but not the golf course. And it's starting to get awfully hot outside.

[Read more here]

One obvious solution is to plant trees in cities.  This would reduce urban temperatures by 5 degrees C.  Another solution is installing solar panels, because their output comes during the day when temperatures are highest.  And to cover the need for air conditioning at night, add 12 hours of storage.  The problem right now is that batteries are supply-constrained, but that won't last forever.  And finally, regulations are needed to make all new buildings more energy efficient.