Some commonly used heating systems are heat pumps, boilers, natural gas furnaces, and electric baseboard heaters, all of which have varying efficiencies, costs, and greenhouse gas emissions. In comparison, heat pumps have higher installation costs, however, they come with the benefit of lower operating costs.
How do heat pumps work?
There are many kinds of heat pumps, such as air-to-air heat pumps, air-to-water heat pumps, and geothermal heat pumps. All these systems work similarly; the heat pump absorbs heat from the surroundings and directs it into the desired space. In the air-to-air and air-to-water source, the first heat exchanger, which is ideally attached to the outer side of a home, absorbs heat from the air outside, the refrigerant compresses the air to increase the temperature.
The second heat exchanger heats air or water and directs heat inside the building. Geothermal heat pumps, which are getting more popular in Europe, have the heat exchanger filled with heat exchanger fluid and are located below the ground surface. In the winter, the outside temperature is cooler than the below ground.
The heat exchanger brings the warm air to the heat pump, situated overground. The heat pump makes the air warmer and circulates it around the house. In summer, it works in reverse.
Adaptation of heat pumps around the world
Heat pumps have gained more attention around the world in the last two decades. Initially, they were primarily chosen as a solution for heating homes, but with time, it has become clear that the application can be utilized widely in buildings, family homes, non-residential buildings, and many more. The use of ground-based heat pumps has particularly gained huge attention as in the last two decades, their consumption has increased by 10% per year.
With the continuous growth of the construction industry, China’s positive response towards the adaptation of energy-efficient and environmentally friendly heating and cooling system led to the use of geothermal energy and reached installation in around 841 million square meters in 2019, making China the first in the world. In Beijing, the government provides 30% of the initial investment cost to encourage the installment.
Currently, in the EU, the building sector accounts for 40% of energy use, of which heating represents the largest share. This energy consumption is equivalent to 36 % of the greenhouse gas emissions.
The EU expects the increase of space heating in residential buildings to around 12% in 2030 and 34% in 2050, compared to 4% in 2015. With this, the market share of heat pumps will also increase. In the UK, the use of a heat pump can help save up to £1,300 ($1500) a year. The UK government has a target to install at least 600,000 heat pumps each year by 2028. The plan is also to wipe out the installation of gas boilers by 2035. To promote the plan, £5,000 grants are offered for the installation of heat pumps.
In Germany, the ‘Federal Funding for Efficient Buildings’ programme started in the summer of 2021, awarding loans and grants worth almost €27 billion for almost half a million residential units. In the other part of the world, the United States currently offers a 26% federal tax credit for new residential ground source heat pumps until the end of 2022, which will decrease to 22% in 2023.
Is heat pump good for the environment?
Already more than a decade ago, the team modeled and evaluated the performance of a heat pump system that undertook a low-temperature geothermal resource and demonstrated the energy and exergy efficiency of the system to be 73.9-73.3% and 63.3-51.7%, respectively.
Heat pumps are also considered to be energy-efficient dryers because they have precise control of gas humidity and temperature. The advantages of heat pump dryers are that it offers the highest specific moisture extraction ratio, improve dried product quality at low temperatures, and allow wider drying conditions, ranging from 15-80% relative humidity and 20-100°C auxiliary heating.
However, the environmental evaluations of heat pumps largely depend on the indirect emissions from the electricity usage as well as direct emissions of the refrigerant. With the use of electricity from a renewable energy source, heat pumps have the advantage of using less energy, which means fewer emissions from direct use.
In a comparative study conducted in three cities in Canada, heat pumps were found to consume four times less annual fuel than natural gas furnaces and electric baseboards. A theoretical study was carried out by a research team at the University of Texas, by using heat pumps on 400 locally representative single-family homes in each of 55 cities. The team stated that installing heat pumps would avoid $1.7 billion in climate damages each year.
In 2020, a paper compared the potential environmental impact of heat pumps with gas boilers. Their results demonstrated that greenhouse gas emissions of air source heat pump, ground source heat pump, and boiler are 0.111 kg CO2e, 0.097 kg CO2e, and 0.241 kg CO2e, respectively.
As most countries are targeting Net-Zero by 2050, it requires a huge commitment. The adaptability of heat pumps is one of the sustainable choices that can contribute to achieving this goal, but it requires massive support from the government around the world.
