Ground Source Heat Pump

Overview

Heat pumps take heat from the external environment and distribute that heat throughout your home. Ground Source Heat Pumps are underground systems which use electricity to extract heat from the ground to heat up your home.

What is a Heat Pump?

A heat pump is a system that utilises mechanical work to move heat from a cold location to a hot location. This is made possible by an external heat exchanger, which collects heat from the environment, and an internal heat exchanger, which distributes the heat into the home with the help of a compressor.

The efficiency of a heat pump is a crucial parameter in determining the savings it can offer. The Coefficient of Performance of a heat pump, or COP, is a commonly used measure for assessing heat pump performance. The COP showcases how many units of heat are produced per unit of electricity used by the compressor. For example, a COP of 3 means that 3 watts of heat are produced for each watt of electricity consumed.

What is a Ground Source Heat Pump?

A Ground Source Heat Pump, or GSHP, is a distinct type of heat pump which relies on heat collection from the ground. They can be used for both water and space heating. A GSHP has on average, a Coefficient of Performance (COP) of 3.5 to 4.5. While ASHPs can be retrofitted to a domestic property at any time, ground source heat pumps are more suited to new builds due to infrastructural constraints.

There are two types of ground source heat pumps, the open loop system, and the closed loop system. An open loop GSHP system relies on access to a groundwater source, from where it extracts heat, while a closed loop GSHP system extracts heat directly from the ground. The closed loop GSHP system is most common for domestic heating purposes, as it does not require proximity to a body of water. There are two types of closed loop GSHP systems:

• Horizontal GSHP: For this type of GSHP, a network of copper or plastic tubes is buried underground horizontally at a depth of 1-2 m. This method is common for properties which have more land available, as a horizontal ground source heat pump system requires a land area 2 to 4 times larger than the domestic floor area. Therefore, for the average 150 m² home, between 300-600 m² of land area is required.
• Vertical GSHP: For this type of GSHP, vertical boreholes, 6 m deep on average, are used to lay the pipes. Vertical boreholes are a more expensive alternative to the horizontal system. Vertical GSHPs are more suitable for urban and suburban areas where space is limited.

Advantages

• Energy-efficient: GSHPs are one of the most energy-efficient water heating systems.
• Reasonable Unit Costs: Although more expensive than conventional heating systems, GSHPs are among the cheapest carbon-free heating solutions. The cost of an GSHP in the UK is typically in the region of £2500 – £5000.
• Low Operational Costs: Depending on the COP, a GSHP can be much cheaper to run than alternatives such as full electric systems or gas boilers.
• Less Maintenance: GSHPs require less maintenance compared to combustion-based heating systems.
• Carbon Emission Reduction: A GSHP produces no carbon emissions on site, as no fuel is burned in the process. If the electricity used by an GSHP is from renewable sources, then the process is carbon free.
• Long Lifespan: Longer lasting components compared to ASHPs.
• Less Noise: GSHPs are less noisy than ASHPs and gas boilers.
• Incentives: Eligibility for the Renewable Heat Incentive scheme.

Disadvantages

• Less Flexibility: GSHPs are not ideal for retrofits as they are normally located below ground underneath the property.
• Space Requirement: Horizontal GSHP systems require a large area of land to be implemented.
• Geology Dependant: GSHPs can only be implemented in certain types of terrain.
• High Installation Costs: GSHPs are similar to air source heat pumps in terms of unit costs. However, the additional labour for laying ground pipes raises the total installation cost to £9,000 - £17,000.

Electric Boiler

Overview

Electric boilers are an efficient and popular heating technology which represent a good alternative to gas boilers. An electric boiler differentiates itself from regular gas boilers through using electricity to operate rather than combustible fossil fuels.

What is an Electric Boiler?

The way an electric boiler produces heat is very simple; water flows through an element of the boiler which is heated using electricity. After running through the boiler, the water passes through the heating systems in your home, such as radiators and underfloor heating, therefore increasing the temperature.

Electric boilers are usually mounted on the wall, or placed on the floor in your home. Although electric boilers can be used as standalone heating sources for homes, this technology is commonly used as a booster for central heating systems, especially during colder months.

Advantages

• Silent: The inner components of electric boilers operate at a slow pace, allowing the boiler to produce heat in near silence.
• Energy Efficient: Although not as efficient as heat pumps, most electric boiler models reach an efficiency close to 100%.
• Environmentally Friendly: Electric boilers do not burn fossil fuels, therefore reducing the carbon footprint of your home. If the electricity used to operate the electric boiler is from renewable sources, then the process is carbon free.
• Low Installation Cost: As the electric boiler does not need to be connected to the gas network, the installation costs are less than for a gas boiler.
• Low Capital Cost: Electric boiler models are in the range of £1,500 – 2,000.
• Low Maintainance: Electric boilers are not mechanically complex; therefore, they do not require intensive maintenance.

Disadvantages

• Home Size Limitation: Electric boilers are not suitable for larger properties, as they cannot produce enough heat to keep up with demand.
• Power Cuts: As they operate using electricity, electric boilers do not produce heat during a power cut.
• High Operational Costs: The price of electricity is higher than the price of gas, therefore an electric boiler is more expensive to run than a gas boiler.

Hydrogen Boiler

Overview

Hydrogen boilers are seen as the simplest solution to the nation’s heating problems by industry experts. Hydrogen boilers are adapted gas boilers which produce heat through burning a mixture of hydrogen and natural gas. Although uncommon, hydrogen boilers are perceived as the future of domestic heating in the United Kingdom, since they are a carbon free alternative. However, their uptake is dependent upon a large-scale switch in domestic supply from natural gas to hydrogen.

What is a Hydrogen Boiler?

Simply put, a hydrogen boiler is a repurposed gas boiler, which can burn either natural gas, or pure hydrogen. Hydrogen is an alternative fuel to methane and differentiates itself by producing no carbon emissions upon consumption.

Converting a conventional gas boiler into a hydrogen-ready boiler is a simple process lasting around one hour, as only a couple of components need to be changed. The conversion can only be done by gas engineers trained to work with hydrogen by a qualification scheme!

What is Hydrogen?

Hydrogen is the simplest of all elements in the periodic table. It is made from only one proton and one electron. This means that hydrogen rarely exists by itself and is instead combined with other elements, such as oxygen to form water. Hydrogen represents a clean energy source which, when extracted from various sources, can serve as a fuel for domestic heating. There are three types of Hydrogen:

• Green Hydrogen: Green hydrogen is obtained when passing a high current through water, resulting in the separation of oxygen and hydrogen atoms, a process referred to as electrolysis. This process is costly, as large amounts of electricity are needed to separate the two elements. The obtained hydrogen is called green hydrogen, as no CO₂ is emitted if the used electricity stems from renewable sources.
• Blue Hydrogen: Blue hydrogen is obtained by two processes: steam-methane reforming and Carbon Capture Utilisation Storage (CCUS). Steam-methane is a process of separating the carbon and hydrogen in methane, resulting in a large quantity of emissions. Therefore, CCUS systems are used to prevent carbon from being released into the atmosphere. Higher quantities of hydrogen can be produced through steam-methane reforming than through electrolysis.
• Grey Hydrogen: Similarly to blue hydrogen, grey hydrogen is produced through steam-methane reformation. However, in this case CCUS technology is not used, resulting in carbon dioxide and carbon monoxide emissions.

Advantages

• Renewable: Hydrogen is a renewable energy source, available all around us.
• Clean Energy Source: Burning hydrogen does any carbon dioxide.
• High Efficiency: Using hydrogen as an energy source provides 2 to 3 times more power than burning the equivalent amount of fossil fuels.
• Low Capital Costs: Hydrogen boilers should cost the same amount as conventional gas boilers.
• Familiarity: As hydrogen boilers are repurposed gas boilers, this is a familiar technology to homeowners.

Disadvantages

• Volatility: Hydrogen is very flammable, meaning it is a potential fire hazard.
• High Operational Costs: Hydrogen is expensive to produce, especially in the case of green hydrogen. This results in high operational costs for hydrogen boilers. However, these costs are expected to decrease with time, as hydrogen boilers become increasingly popular.
• Unproven Technology: Although hydrogen boilers seem to be a viable solution for the domestic heating problem, there is a severe lack of infrastructure for them to be adopted at scale. Hydrogen heating technology is still young and unproven.

Hydrogen Fuel Cell

Overview

Hydrogen fuel cells use chemical energy from hydrogen to produce electricity. Hydrogen fuel cells produce clean energy, as their only by-products are water, heat, and most importantly, electricity. This technology has a variety of applications, one of which is domestic heating. Hydrogen fuel cells represent a simple and viable heating alternative for the UK market, as this technology is cleaner and more efficient than conventional solutions such as gas boilers.

What is a Hydrogen Fuel Cell?

A hydrogen fuel cell works similarly to a battery. Unlike a battery, they do not need to be recharged if the fuel (hydrogen) is supplied. Each hydrogen fuel cell has an electrolyte membrane and two electrodes: an anode (negative), and a cathode (positive). The reaction that produces electricity happens between these electrodes and consists of the following steps:

1. Hydrogen atoms are distributed to the anode, while oxygen atoms are distributed to the cathode.
2. The hydrogen atoms are separated into protons and electrons.
3. While the protons move towards the cathode, the electrons are forced through a circuit in order to generate electricity.
4. While the protons move towards the cathode, the electrons are forced through a circuit in order to generate electricity.

Single hydrogen fuel cells do not produce enough electricity to supply a domestic property. Therefore, for domestic heating purposes, they need to be arranged into stacks.

What is Hydrogen?

Hydrogen is the simplest of all elements in the periodic table. It is made from only one proton and one electron. This means that hydrogen rarely exists by itself and is instead combined with other elements, such as oxygen to form water. Hydrogen represents a clean energy source which, when extracted from various sources, can serve as a fuel for domestic heating. There are three types of Hydrogen:

• Green Hydrogen: Green hydrogen is obtained when passing a high current through water, resulting in the separation of oxygen and hydrogen atoms, a process referred to as electrolysis. This process is costly, as large amounts of electricity are needed to separate the two elements. The obtained hydrogen is called green hydrogen, as no CO₂ is emitted if the used electricity stems from renewable sources.
• Blue Hydrogen: Blue hydrogen is obtained by two processes: steam-methane reforming and Carbon Capture Utilisation Storage (CCUS). Steam-methane is a process of separating the carbon and hydrogen in methane, resulting in a large quantity of emissions. Therefore, CCUS systems are used to prevent carbon from being released into the atmosphere. Higher quantities of hydrogen can be produced through steam-methane reforming than through electrolysis.
• Grey Hydrogen: Similarly to blue hydrogen, grey hydrogen is produced through steam-methane reformation. However, in this case CCUS technology is not used, resulting in carbon dioxide and carbon monoxide emissions.

Advantages

• Renewable: Hydrogen is a renewable energy, available all around us.
• Clean Energy Source: The electrochemical reaction of hydrogen does not produce any emissions.
• High Efficiency: Using hydrogen as an energy source provides 2 to 3 times more power upon reaction than fossil fuels.

Disadvantages

• Volatility: Hydrogen is very flammable, making it risky to work with.
• High Operational Costs: Hydrogen is expensive to produce, especially in the case of green hydrogen. This results in high operational costs for hydrogen boilers. However, these costs are expected to decrease with time, as hydrogen boilers become increasingly popular.
• Unproven Technology: Although hydrogen fuel cells seem to be a viable solution for the domestic heating problem, this technology is still young and unproven at a large scale.
• High Capital Costs: Hydrogen fuel cells can be expensive due to the use of platinum as a main material.

Biomass Boiler

Overview

Biomass Boilers are a similar technology to conventional gas boilers, but they use biomass such as sustainable wood pellets as their fuel source instead of methane. Using wood from landfill sources as fuel has an important environmental impact, as the carbon dioxide emissions produced during combustion are compensated for by the CO2 absorbed by the tree while it was growing. Therefore, biomass boilers are essentially carbon neutral. Biomass boilers are a viable domestic heating alternative to conventional gas boilers according to industry experts.

What is a Biomass Boiler?

A biomass boiler works in a similar way to a conventional gas boiler: fuel is burned to produce heat. The key difference between a biomass boiler and their fossil-fuel counterparts is in the fuel that's used. Given the fuel source difference, biomass boilers are significantly larger than conventional boilers. This is because the combustion chamber needs to be larger in order to accommodate the volume of the biomass.

Biomass boilers can come with systems that automatically feed biological materials into the combustion chamber, or this can be done manually by the homeowner. Biomass combustion produces hot gasses and air, which travel to a heat exchanger. Here, the heat is transferred to the water used in the property’s central heating system. It is important to understand that a biomass boiler is different from a traditional chimney!

Biomass Fuel Types

Biomass is a term that refers to any type of organic matter. In an energy context, biomass is any organic matter than can be used to generate energy. There are various types of biomass fuel available, with different costs and efficiencies. The following biomass types are used as fuel for biomass boilers:

• Wood Chips: This is the cheapest type of biomass fuel and is best suited for medium to large scale biomass boilers.
• Wood Pellets: This biomass type is made from the excess material collected at wood processing facilities, and is slightly more expensive than wood chips. As wood pellets are dense and compact, this is the most efficient form of biomass fuel.
• Logs: Logs can be expensive unless you have free access to wood. Moreover, logs need spacious storage facilities.
• Non-Wood Biomass: Agricultural waste such as wheat and straw can be used as fuel in biomass boilers.

Each year, approximately 8.5 million tonnes of wood goes to landfill in the UK. This could be used to fuel biomass boilers.

Advantages

• Renewable: Biomass is a fuel that can be regenerated quickly by growing plants and trees.
• Carbon Neutral: The carbon dioxide absorbed by growing plants is then burnt when using biomass fuels. This cycle is repeated, meaning no new carbon is released into the atmospshere. Therefore, biomass fuels are considered carbon neutral.
• Waste Reduction: Biomass boilers help dispose of wood waste.
• Low Operational Prices: The price of biomass fuel is considerably lower than the price of gas or electricity.
• Incentives: Biomass boilers qualify for the Renewable Heat Incentive scheme, which helps homeowners repay their initial investment.

Disadvantages

• Additional Space: Biomass boilers are larger than conventional boilers, meaning they require more space. Moreover, homeowners also need storage facilities for biomass fuel.
• High Capital Costs: Biomass boilers are more expensive than conventional gas boilers. Biomass boilers also have higher installation costs.
• Ideal Storage Conditions: Biomass fuel requires optimal storage conditions as it needs to remain dry in order to burn efficiently.
• Less Convenient: Biomass boilers require more work from homeowners, as the fuel needs to be supplied continuously (unless an automated hopper system is used).
• Cleaning: Biomass boilers need to be cleaned on a regular basis (about once every week).
• Need for a Supplier: Homeowners opting for a biomass boiler need to have their biomass fuel delivered on a regular basis by an independent supplier.