6 minute read
Heat Pumps
HEAT PUMPS: LOWERING CARBON AND COSTS
The UK has reduced greenhouse gas emissions by 43% compared to 1990, thanks to the rigorous and impactful Climate Change Act. Currently celebrating its tenth birthday, the Climate Change Act was launched in a bid to set a binding emissions target for the UK by 2050. Ensuring that the UK continues to build on the strong foundations set in previous years and remains on track to meeting the third carbon budget will require a concerted effort across all industries. However, certain sectors will require significant attention.
Energy use in the built environment is one of the most important aspects that must be addressed in the UK and
Figure 1: Heat pumps work by absorbing heat from a cold space and releasing it to a warmer one abroad in the near future. Around 40% of the primary energy use within Europe is related to the building sector, with buildings accounting for 34% of carbon emissions in the UK. Among the key drivers of investment in efficiency include carbon reduction, fuel poverty alleviation and cost savings. The major challenge lies in the decarbonisation of heat. The UK has a particularly rigorous framework for achieving decarbonisation, and the decarbonisation of heat will become increasingly important in the coming years. Nevertheless, doing so will be an arduous task. Decarbonisation policies up to now have mainly affected electricity, leading to fundamental changes and challenges for the sector. It is now time for heat to follow suit.
One of the most promising technologies aimed at increasing efficiency and reducing emissions in the building sector is provided by electric heat pumps. Heat pumps offer a modern, low-carbon solution to provide space heating and domestic hot water and are particularly appropriate in countries that have both high heating requirements (in winter) and cooling requirements (in summer).
At the time of writing, there are 11,279,386 installed in Europe, saving 29.8 million tCO2, producing 116 TWh of renewable energy and providing 60,000 jobs.
WHAT IS A HEAT PUMP AND HOW DOES IT WORK?
A heat pump is an electrical device that extracts heat from one place and transfers it to another. Heat pumps are a highly efficient way to heat buildings. They draw in heat from the environment and use electricity to raise the temperature to a suitable level for space heating and hot water. Typically for each kWh of electricity consumed, 2.5-4kWh heat is supplied. Heat pumps deliver lower temperatures than boilers, so they work well with underfloor heating in new buildings or radiators with a larger surface area.
The most conventionally applied heat pump is the mechanical heat pump, which is based on the compression and expansion of a working fluid, or ‘refrigerant’. Heat pumps transfer heat by circulating the refrigerant through a cycle of evaporation and condensation. A heat pump comprises four main components: evaporator, compressor, condenser and expansion device. The
Figure 2: Air-source heat pumps have small physical footprints, though they need to be positioned somewhere with adequate airflow.
refrigerant is pumped by a compressor between two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed en-route to the other coil, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.
There is a range of heat pumps on the market, and how you choose it will depend on several factors, such as energy requirements, current building heating infrastructure and site characteristics. Heat pumps can be divided into two broad sub-categories: air-source and geothermal (ground-source).
AIR SOURCE HEAT PUMPS
Air-source heat pumps extract heat from the outside air, operating like fridges in reverse. These heat pumps in a residential setting can save more than 2 tonnes of carbon per year, contributing up to 20% less CO2e than gas boilers and up to 70% less than electric systems. As well as providing a heat source in winter, the cycle is fully reversible in the summer, allowing heat pumps to provide year-round climate control. This technology can be an efficient means of saving money and saving carbon emissions if carefully designed and specified for the appropriate buildings.
GROUND-SOURCE HEAT PUMPS
Conversely, ground-source heat pumps transfer heat from the ground into a building. A ground-source heat pump system needs land available to lay heat collectors in the ground – either laterally in trenches, or vertically in boreholes. The basic elements of a ground source heat pump system are the heat pump itself, the ground loop and the distribution system. A significant advantage of using a groundsource system over an air-source equivalent is the higher coefficient of performance in the winter, as the temperature in the ground is higher than the ambient air temperature.
ARE HEAT PUMPS AN EFFECTIVE SOLUTION FOR UK BUSINESSES?
These technologies are wellestablished and widely used in the UK and backed by attractive government incentives. The Renewable Heat Incentive (RHI) is a government environmental programme that provides financial incentives aimed at increasing the uptake of renewable heat by businesses, the public sector and non-profit organisations. Eligible installations receive quarterly payments over 20 years based on the amount of useful heat generated.
Heat pumps are a great alternative to many of the current carbon-intensive heating methods and represent a smart long-term investment for businesses and households alike. However, it is worth considering the below before installing your new system.
Before purchasing this technology, it is important to assess the associated benefits and costs. While these systems have lower fuel costs than conventional heating systems, they have a sizable upfront installation cost which often proves as a barrier to SMEs. Taking the following considerations will allow businesses to pick up the most suitable system for your needs: • Placement: An air-source heat pump requires plenty of space, whether it is wall or groundmounted. Ground-source systems will require significant land area and are also likely to be subject to strict planning regulations. Nevertheless, heat pumps are far more flexible from a placement point of view than gas boilers and indeed most renewable energy technologies. • Cost of air source heat pump system vs current heating infrastructure: Heat pumps can markedly reduce energy costs when in place of conventional electric heating, as well as expensive fuels like oil, LPG or coal. Savings over traditional central heating are however less significant due to the low cost of gas. • Insulation: Heating only works if the heat can be retained. It is important to ensure that the proposed building is suitably energy-efficient. Investing in low-cost insulative measures like improved building fabric and window glazing will help to keep the heat in and maximise heat pump efficiency.
Despite this, research indicates that around 22,000 heat pumps were installed in the UK in 2017, which represents an increase of 18% in volume compared to the previous year.
This increase has been brought about by the realisation of the various benefits of this technology, including: • Reduced fuel bills and carbon emissions • Minimal maintenance required • No fuel deliveries needed • Income through the government’s
Renewable Heat Incentive (RHI) Energy efficiency measures have the potential to deliver the sizeable emissions cuts needed to meet the targets set by the Climate Change Act. Technologies like heat pumps represent low-hanging fruits for both businesses and households in the UK and abroad.
While they may not be for everyone, heat pumps represent a modern, costeffective solution to reducing both your energy costs and carbon footprint.
We at Avieco are energy experts, working with organisations like yours to map your energy impacts, identify areas to prioritise, and build the case for improving your performance in energy productivity, ultimately helping you becoming more sustainable. www.avieco.com
Figure 3: Ground-source heat pumps require a larger site for installation
