What are the best technologies to heat homes cleanly?

Solar thermal systems

Another option is to heat buildings with the sun through solar thermal technology. Unlike solar photovoltaic systems, where panels turn sunlight into electricity, solar thermal systems absorb sunlight to heat water, which is then pumped around a building.

In 2020, 250 million dwellings used solar thermal technologies for water heating, according to the International Energy Agency, a Paris-based organization led by the energy ministers of mostly rich countries. In its net zero emissions scenario, it expects 400 million to be needed by the end of the decade. Because some older systems will need to be retired, the agency expects 290 million new solar thermal systems will need to be installed this decade.

Solar thermal technologies can cheaply heat high fractions of water heating demand at low capital cost, even in cold climates, according to the IEA, and can be integrated into all types of heating systems. While some buildings can be heated entirely this way, solar thermal technologies require large water storage systems that make them less practical as the sole heat source.

It’s a complementary heat source, said Rosenow. “It’s not a standalone system unless you have those really big storage devices in place.”

Biomass

The most popular renewable form of heating in Europe is also one of the least sustainable: burning biomass.

By heating homes directly with wood pellet boilers — or indirectly via biomass-fuelled district heating plants — buildings can be kept warm without using up finite resources in theory. Burning trees can be considered carbon-neutral if they are replanted, because the CO2 released during combustion will be sucked back in by photosynthesis.

But in practice, the carbon in the atmosphere heats the planet while it is up there, and it takes decades for a felled forest to grow back. What’s more, the land on which the trees are grown cannot be used for anything else, and is in short supply.

In the EU, the biggest increases of renewables in heating have taken place in countries where biomass is a key source of heat. This figure is partly distorted because it is measured by the total amount of heat generated, rather than the useful share. That makes an efficient heat pump seem less desirable than an inefficient boiler, according to an analysis from the Regulatory Assistance Project, giving countries an incentive to chase renewable targets by burning biomass instead of electrifying.

An analysis in 2017 from the World Resources Institute, an environmental nonprofit, criticized the EU’s weak sustainability criteria for biomass. “If the EU does not restrict biomass to genuinely CO2-friendly feedstocks, other countries will likely adopt similarly lax regulations that allow trees to be used as renewable energy sources—with significant negative consequences for forests and climate.”

In the IEA’s net zero scenario, burning biomass provides 10% of the heat used globally in 2030 and 20% in 2050.

Biomethane

Another way of using organic matter to heat homes is to turn it into gas.

When bacteria digest plant matter without air — for instance, on a landfill site — they release methane. The gas is the main component in fossil gas, also known as natural gas, and has a powerful effect on the climate. Methane heats the planet 80 times more than CO2 over a 20-year-period, though it does not last as long in the atmosphere.

By purifying the methane produced this way — stripping out the CO2 and other contaminants — scientists can produce biomethane, a fuel nearly indistinguishable from natural gas. The feedstocks are usually unwanted byproducts of other key processes: crop residues, animal manure, the organic part of household waste, and wastewater sludge. In some countries like Germany, though, crops are grown specifically for energy — raising concerns the land could be put to better use.

But to heat homes, experts say, the amount of biomethane available from sustainable sources is unlikely to add up to much. The gas industry is keen to use what is available as a cleaner fuel to heat homes without dismantling boilers and pipes inside homes. But environmental groups fear that doing so will delay the switch to clean infrastructure.

SDGs, Targets, and Indicators

Solar thermal systems

• SDG 7: Affordable and Clean Energy
• Target 7.2: Increase the share of renewable energy in the global energy mix.
• Indicator 7.2.1: Renewable energy share in the total final energy consumption.

The article discusses the use of solar thermal systems for heating buildings, which aligns with SDG 7 on Affordable and Clean Energy. The specific target under this SDG that can be identified is Target 7.2, which aims to increase the share of renewable energy in the global energy mix. The article mentions that solar thermal technologies can be used to heat water in buildings, providing a renewable energy source for heating. The indicator that can be used to measure progress towards this target is Indicator 7.2.1, which measures the renewable energy share in the total final energy consumption.

Biomass

• SDG 7: Affordable and Clean Energy
• Target 7.2: Increase the share of renewable energy in the global energy mix.
• Indicator 7.2.1: Renewable energy share in the total final energy consumption.

The article also discusses the use of biomass for heating, which is a popular renewable form of heating in Europe. This aligns with SDG 7 on Affordable and Clean Energy. The specific target under this SDG that can be identified is Target 7.2, which aims to increase the share of renewable energy in the global energy mix. The indicator that can be used to measure progress towards this target is Indicator 7.2.1, which measures the renewable energy share in the total final energy consumption.

Biomethane

• SDG 7: Affordable and Clean Energy
• Target 7.2: Increase the share of renewable energy in the global energy mix.
• Indicator 7.2.1: Renewable energy share in the total final energy consumption.

The article also mentions the use of biomethane as a way to heat homes. This aligns with SDG 7 on Affordable and Clean Energy. The specific target under this SDG that can be identified is Target 7.2, which aims to increase the share of renewable energy in the global energy mix. The indicator that can be used to measure progress towards this target is Indicator 7.2.1, which measures the renewable energy share in the total final energy consumption.

Table: SDGs, Targets, and Indicators

The table presents the findings from analyzing the article, listing the relevant SDGs, their corresponding targets, and the specific indicators identified. In this case, all the identified issues align with SDG 7 on Affordable and Clean Energy, specifically Target 7.2 to increase the share of renewable energy in the global energy mix. The indicator used to measure progress towards this target is Indicator 7.2.1, which measures the renewable energy share in the total final energy consumption.

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Source: cleanenergywire.org

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