Low and zero carbon technologies

Low and zero carbon technology (LZC) is the term given to technologies that emit low levels of CO2 emissions, or no net CO2 emissions.

The incorporation of these technologies is more effective within buildings with a highly energy efficient fabric after heat demand and loss have been reduced to a minimum. When used in this way, LZC technologies can bring a building's CO2 emissions closer to zero.

There are a number of technologies that can be used to provide heat for a building, emitting low or no net CO2 emissions.

Some of these technologies can be provided via communal systems.

There is also information and advice on carbon neutrality and compensation options available for new residential development involving three or more units.

Take a look at relevant policies.

Solar hot water

These systems use collectors on the roof to absorb solar radiation and convert it to heat, which then transfers to a hot water cylinder warming up the water in the tank throughout the day.

Solar water heating in the average home with a south facing roof could produce around a third of the hot water needed in a home throughout the year. Therefore, it needs to be installed alongside an auxiliary water heating system, such as normal condensing boiler or biomass boiler.

It is important to makes sure conditions for installing these systems are appropriate in order to achieve the maximum savings.

In order to optimise savings, building users need to be aware that the the best time to use their auxiliary water heating system is after the main warmth of the day and before their first major use of hot water. 

For further information on this technology Energy Saving Trust website.

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

Air source heat pumps (ASHP)

These absorb heat from the outside to heat buildings. There are two types of air-source heating systems: air-to-air and air-to-water. 

Air-to-air systems provide warm air, which is circulated to heat the building via fans. They are most suited to units with no or little hot water requirement such as retail outlets.

Air-to-water systems heat water to provide heating to a building through the distribution system - radiators or an underfloor system. Some air to water heat pumps come with a mechanical whole house ventilation system with heat recovery - these are called exhaust air source heat pumps. These pumps recover the heat from the stale damp air from wet rooms and use the heat to preheat fresh incoming air to the living rooms and bedrooms. This recovered heat contributes to the heating load and removes the need for any other mechanical ventilation system. The heating, hot water storage and ventilation system is packaged together in one compact unit. It is only suitable for smaller units with lower heat loads and hot water requirements, such as three bed houses/flats.

Both types of air source heat pumps produce hot water that is a lower temperature (typically 35-45C) than standard boiler systems. This makes them work more efficiently with underfloor heating where the temperature differential is lower. They can be used with radiators but radiators must be dimensioned (sized larger than required by conventional heating systems) to run at the lower temperature. All ASHPs require an immersion back up.   

For further information on this technology Energy Saving Trust website.

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

Ground source heat pumps (GSHP)

These transfer heat from the earth into the home to provide space heating and hot water through a heat exchange system which works like a refrigerator in reverse. An accurately sized system is able to produce 100% of the heating and hot water requirement of a well insulated home.

GSHPs consist of a ground loop, heat pump and distribution system. The ground loop can be in horizontal trenches, vertical boreholes or in the structural piles of a building. Vertical boreholes and structural piles are used where there is limited external space. GSHP can also be used in reverse for cooling. When the GSHP is used for heating and cooling in a building in the same day, the efficiency of the system is enhanced.

This system is particularly effective in offices where chilled beams are used to distribute the cool air. GSHPs should be considered as a sustainable alternative to air conditioning systems. 

For further information on this technology Energy Saving Trust website

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

Combined Heat and Power (CHP)

Cogeneration (also known as combined heat and power, CHP) is the simultaneous production of electrical energy and useful heat energy from a single energy source. In some cases the energy source can be from renewable or low/zero carbon energy such as solar energy or biomass. 

Through the use of an absorption cooling cycle, trigeneration (combined cooling, heat and power CCHP) schemes can also be developed, thus providing air cooling / conditioning.

Cogeneration systems can be employed over a wide range of sizes, applications, fuels and technologies. In its simplest form, it employs a turbine to drive an alternator, and the resulting electricity can be used either wholly or partially on-site. The heat produced during power generation is recovered, usually in a heat recovery boiler and can be used to raise steam for a number of industrial processes, to provide hot water for space heating, or, as mentioned above with appropriate equipment installed, cooling.

Because cogeneration systems make extensive use of the heat produced during the electricity generation process, they can achieve overall efficiencies in excess of 70% at the point of use. Cogeneration systems are typically installed onsite, supplying customers with heat and power directly at the point of use, therefore helping avoid the significant losses which occur in transmitting electricity from a large centralised plant to customer.

Cogeneration can be used to provide energy to a single home, a large industrial plant or even a whole city. In the home, a micro cogeneration unit resembling a gas-fired boiler will provide both heat for 100% of the space and water heating, as does a boiler, but also electricity to power domestic lights and appliances.

Some building types, particularly those that need a lot of energy, or operate around the clock, are particularly suitable for cogeneration - leisure centres, hotels, hospitals and many others. Homes and buildings fitted with cogeneration are usually connected to the mains electricity grid, and may also retain back-up boilers, so that they are never short of an energy supply. Owing to the erratic electricity demand patterns of dwellings, there will inevitably be some exporting to the grid unless the electricity can be used elsewhere in the vicinity of the development.

Further details can be found on the Carbon Trust website and The Combined Heat and Power Association website

Biomass heating system

The term 'biomass' covers all plant and animal matter on the Earth's surface. Heat, electricity, or automotive energy generated from crops, trees, or agricultural waste, is referred to as 'bioenergy' or ‘biofuel’. Biomass is a manageable fuel source unlike wind or solar and it can be stored and used on demand.  

Woody biomass includes forest products, untreated wood products, energy crops and short rotation coppice (SRC), which are quick-growing trees like willow.

  • Non-woody biomass includes animal waste, industrial and biodegradable municipal products from food processing and high energy crops. Examples are rape, sugar cane, maize.
  • For small-scale domestic applications of biomass the fuel takes the form of wood pellets, wood chips or wood logs. There are two main ways of using biomass to heat a domestic property:
  • Stand alone stoves providing space heating for a single room. These can be fuelled by logs or pellets. Some stoves can be fitted with back boilers to provide water heating.
  • Boilers connected to central heating and hot water systems. These are suitable for pellets, logs or chips, and are generally larger than 15 kW.

There are many domestic log, wood chip and wood pellet burning central heating boilers available. Log boilers must be loaded by hand and may be unsuitable for some situations. Pellet and wood chip systems can be fully automated and are more expensive. Many boilers will dual fire both wood chips and pellets, although the wood chip boilers need larger hoppers to provide the same time interval between refuelling. This makes wood pellet systems more attractive for urban areas. Wood can only be burnt in exempted appliances in smokeless zones and it is more sustainable to buy locally sourced wood fuel as it minimises transport miles. All biomass systems need to have ash removed at fairly regular intervals and need to be maintained like a conventional boiler.

Biomass boilers are more efficient when operating at maximum capacity. This means they work well with solar panels which can produce hot water during summer months when space heating is not required and the boiler can be switched off.  Some biomass boilers installed with a thermal water store can be combined with any other source of heating from traditional gas condensing boilers and solar hot water panels. This allows the occupant to choose when to use biomass to heat their home and provide hot water.    

For further information on this technology Energy Saving Trust website. For further information on Sustainable Heating Technologies A review of microgeneration and renewable energy technologies [PDF 216MB]

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

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Efficient gas boiler

A high efficiency gas condensing boiler works on the principle of recovering as much as possible of the waste heat which is normally wasted from the flue of a conventional (non-condensing) boiler. The best high efficiency condensing boilers convert more than 90% of their fuel into heat, compared to 78% for conventional types.

There are two types of condensing boiler - a regular condensing boiler which stores hot water in a tank, and a combination condensing boiler which provides instant hot water. If you are planning to install solar hot water panels at the same time or at a future date you will need to fit a regular condensing boiler as a water store is required. If the boiler is an A-rated boiler according to SEDBUK ratings then it is a high efficiency condensing boiler.

For futher details see the following document Domestic condensing boilers-the benefits and the myths [PDF 455kb] and the Energy Saving Trust website. For infromation on efficient equipment and controls see The Carbon Trust website.

Solar photovoltaics (PV)

Photovoltaic (PV) systems require daylight (not direct sunlight) to generate electricity. They come in a variety of shapes and colours, ranging from grey 'solar tiles' that look like roof tiles, to panels and transparent cells that you can use on conservatories and glass to provide shading as well as generating electricity.

They are most suitable for buildings with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, the output of the system decreases. PV panels are not light and the roof must be strong enough to take their weight, especially if the panel is placed on top of existing tiles.

Because PVs are versatile, PV arrays bear potential for use in buildings in conservation areas and listed buildings.

For further information on this technology Energy Saving Trust website.

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

Wind turbines

Turbines can be pole mounted on the ground using strong foundations or roof mounted. Studies on roof mounted turbines have shown that they do not perform effectively in most urban environments. Assessment of the effectiveness of location and sitting of turbines is crucial to secure performance.

Influencing factors when considering wind power systems are:

  • Sites should be monitored for at least one year to assess the sites potential for a turbine. High speed winds are required generally at least 5m/s. The British Wind Energy Association database provides data on wind energy by location: http://www.bwea.com/noabl/index.html. 
  • Taller masts are more effective
  • Turbines should be located away from buildings as they can be noisy
  • Price and planning permission may prohibit installations    
  • Connection to the grid should be made to provide top-up when the building demands more energy than the turbine can provide and to allow excess to be exported to the grid. In order to connect to the grid, the system must comply with engineering recommendations.
  • Meters are required to measure energy production so that ROCs or green revenue can be collected on commercial projects and energy exported from homes allowing revenue to be earned.

For further information on this technology Energy Saving Trust website.

For planning advice relevant to Brighton & Hove PAN02 Microgeneration.

Combined heat and power (CHP)

These are also know as cogeneration, involving the simultaneous production of electrical energy and useful heat energy from a single energy source. In some cases the energy source can be from renewable or low/zero carbon energy such as solar energy or biomass. 

Through the use of an absorption cooling cycle, trigeneration (combined cooling, heat and power CCHP) schemes can also be developed, thus providing air cooling / conditioning.

Cogeneration systems can be employed over a wide range of sizes, applications, fuels and technologies. In its simplest form, it employs a turbine to drive an alternator, and the resulting electricity can be used either wholly or partially on-site. The heat produced during power generation is recovered, usually in a heat recovery boiler and can be used to raise steam for a number of industrial processes, to provide hot water for space heating, or, as mentioned above with appropriate equipment installed, cooling.

Because cogeneration systems make extensive use of the heat produced during the electricity generation process, they can achieve overall efficiencies in excess of 70% at the point of use. Cogeneration systems are typically installed onsite, supplying customers with heat and power directly at the point of use, therefore helping avoid the significant losses which occur in transmitting electricity from a large centralised plant to customer.

Cogeneration can be used to provide energy to a single home, a large industrial plant or even a whole city. In the home, a micro cogeneration unit resembling a gas-fired boiler will provide both heat for 100% of the space and water heating, as does a boiler, but also electricity to power domestic lights and appliances.

Some building types, particularly those that need a lot of energy, or operate around the clock, are particularly suitable for cogeneration - leisure centres, hotels, hospitals and many others. Homes and buildings fitted with cogeneration are usually connected to the mains electricity grid, and may also retain back-up boilers, so that they are never short of an energy supply. Owing to the erratic electricity demand patterns of dwellings, there will inevitably be some exporting to the grid unless the electricity can be used elsewhere in the vicinity of the development.

Further details can be found on the Carbon Trust website and The Combined Heat and Power Association website

Community Heating

Community heating schemes (also known as District Heating) provide heat from one central source to multiple buildings. Schemes can range in size from one tower block with a central heat source for all the flats to citywide schemes connecting many public and commercial buildings.Heat sources can include:

  • Conventional boilers using conventional fuel such as gas or oil or renewable fuels (biomass, domestic or agricultural wastes).
  • Combined heat and power (CHP) plant where the heat generated by electricity production is captured and used to generate more electricity or distributed via a heat network.
  • Using waste heat produced from industrial processes, eg distilleries.

The monitoring of actual energy use per dwelling or building, servicing of the plant (emptying the ash in the case of biomass boilers) and billing can be handled by an Energy Service Company (ESCO). Each home or building will require a heat meter and smart card or direct debit arrangement with the ESCO.

For further information see Community Heating-a guide [PDF 818kb].

Carbon neutrality and compesation

Brighton & Hove's SPD08 recommends that all new residential development involving three or more units area are zero carbon or carbon neutral. That is, emit zero net annual CO2 emissions on site or propose measures to compensate for outstanding on-site emissions elsewhere in the city.  

Relevant policies

National policyPPS1: Delivering Sustainable DevelopmentSupplement to PPS1: Climate Change and PlanningPPS22: Renewable energy

Brighton & Hove Local PlanSU2: Efficiency of development in the use of energy, water and materials SU16: Production of renewable energy

Local Development FrameworkSPD08: Sustainable Building Design

Other documentsAffordable Warmth: A Fuel poverty Strategy for residents of Brighton & Hove