Environmental Technologies - City & Guilds Textbook PDF

CHAPTER 1 ENVIRONMENTAL TECHNOLOGIES INTRODUCTION A large number of scientific studies show that climate change is causing more frequent and more extreme weather events around our planet and CO2 emissions are a clear contributor towards this....

CHAPTER 1 ENVIRONMENTAL TECHNOLOGIES INTRODUCTION A large number of scientific studies show that climate change is causing more frequent and more extreme weather events around our planet and CO2 emissions are a clear contributor towards this. The use of energy storage and generating systems, as well as renewable technologies, will help to minimise climate change or its effects by reducing emissions. The construction industry is already going some way to reduce emissions but needs to further promote and utilise these technologies in buildings. Much of the decline in harmful emissions is due to new technologies used in building materials, insulation and renewable energy sources. When working in the electrotechnical sector, you are very likely to come across these technologies. This chapter is intended to explain how they work. HOW THIS CHAPTER IS INDUSTRY TIP ORGANISED The Office for National This chapter is divided up into four sections, each one detailing a type of Statistics’ website updates environmental technology system. figures on CO2 emissions every year. Visit their website to obtain the most current Heat-producing Electricity-producing statistics. Solar thermal Solar photovoltaic Ground-source heat pump Micro-wind Air-source heat pump Micro-hydro Biomass Co-generation Water conservation Micro-combined heat and Rainwater harvesting power (heat-led) Greywater re-use p Figure 1.1 The environmental technology systems covered in this chapter 1 9781398361607.indb 1 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 This approach will help you to understand the working principles of each system and how they impact on the installation requirements and the regulatory requirements. The advantages and disadvantages of each technology system are also described. Note that, for those studying the 2365 Level 3 Diploma in Electrical Installations (Building and Structures) course, you will be formally assessed on your knowledge of environmental technologies as part of the 2365 certification. For those studying: 5357 Electrical Qualification (installation or maintenance) (Apprenticeship) 8202 Level 3 Advanced Technical Diploma in Electrical Installation 8710-353 Electrotechnical Engineering Specialism you will not be formally assessed, but this chapter offers useful information because, in the future, you may be expected to install or advise on environmental technologies. For those studying 8710 T Level Technical Qualification in Building Services Engineering for Construction, this chapter will help with the core unit content (350), especially 5.10 within Outcome 5. q Table 1.1 Chapter 1 assessment criteria coverage Topic 5357 2365 8202 5393-104/004 Regulatory requirements relating 3.1; 3.2 to micro-renewable energy and water conservation technologies Heat-producing micro-renewable 1.1; 2.1; 2.3; 2.4; 2.5; 3.1; energy technologies 3.2; 4.1; 4.2 Electricity-producing micro- 1.2; 2.2; 2.6; 2.7; 3.1; 3.2; 4.4; 7.3 renewable energy technologies 4.1; 4.2 Micro-combined heat and power 1.3; 2.8; 3.1; 3.2; 4.1; 4.2 Water conservation technologies 1.4; 2.9; 3.1; 3.2; 4.1; 4.2 T Level mapping grids are available on the REGULATORY REQUIREMENTS Hodder Education website. These map the RELATING TO MICRO- book to the occupational specialisms: 8710-353 RENEWABLE ENERGY AND WATER (Electrical Engineering) and 8710-352 CONSERVATION TECHNOLOGIES It is important to have knowledge of the planning requirements and building (Electrical and Electronic Equipment). regulations for each technology. This section: explains the terminology used provides insight into the workings of both the planning requirements and building regulations explains the differences in planning regulations across different regions of the UK. 2 9781398361607.indb 2 27/07/22 9:38 PM  Chapter 1 Environmental technologies Planning and permitted development KEY TERMS In general, under the Town and Country Planning Act 1990, before any building Permitted development: work that increases the size of a building is carried out, a planning application Allows certain projects must be submitted to the local authority. A certain amount of building work is, or building work to be however, allowed without the need for a planning application. This is known as carried out without permitted development. the need for planning permission. Permitted development usually comes with criteria that must be met. When building Microgeneration: The an extension, for example, it may be possible to do so under permitted development, small-scale generation if the extension is under a certain size, is a certain distance away from the boundary of heat or electric of the property and is not at the front of the property. If the extension does not power by individuals, meet these criteria, then a full planning application must be made. small businesses and communities to meet Permitted development is intended to ease the burden placed on local authorities their own needs, as and to smooth the process for the builder or installer. Permitted development exists alternatives or in addition for renewable technologies, and this chapter outlines the situations where it applies. to traditional, centralised, grid-connected power, such as power stations. Building Regulations The Climate Change and Sustainable Energy Act 2006 brought microgeneration under the requirements of the Building Regulations. INDUSTRY TIP Even if a planning application is not required, because the installation meets the criteria for permitted development, there is still a requirement to comply with For more information on the relevant Building Regulations. Local Authority Building Control (LABC) is what is allowed as permitted the body responsible for checking that Building Regulations have been met. The development in a typical domestic dwelling, search for person carrying out the building work is responsible for ensuring that approval is the planning portal (England obtained. and Wales) or Planning Portal Building Regulations are statutory instruments that seek to ensure that the NI (Northern Ireland) or policies and requirements of the relevant legislation are complied with. The ePlanning Scotland. Building Regulations themselves are rather brief and, in England, are currently divided into 18 sections, each of which is accompanied by an Approved Document. The Approved Documents are non-statutory and give guidelines on INDUSTRY TIP how to comply with the statutory requirements. You can research the Climate The 18 parts of the Building Regulations in England are: Change and Sustainable Part A Structure Energy Act 2006. Part B Fire safety Part C Site preparation and resistance to contaminates and moisture Part D Toxic substances Part E Resistance to the passage of sound Part F Ventilation Part G Sanitation, hot-water safety and water efficiency Part H Drainage and waste disposal Part J Combustion appliances and fuel-storage systems Part K Protection from falling, collision and impact Part L Conservation of fuel and power Part M Access to and use of buildings Part O Overheating Part P Electrical safety 3 9781398361607.indb 3 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 Part Q Security in dwellings Part R High-speed electronic communications networks Part S Infrastructure for charging electric vehicles Document 7 Materials and workmanship. Compliance with Building Regulations is required when installing renewable technologies. Not all of the Building Regulations will be applicable, however, and different technologies will have to comply with different Building Regulations. The Building Regulations applicable to each technology are indicated in this chapter. HEAT-PRODUCING MICRO- RENEWABLE ENERGY TECHNOLOGIES Some technologies produce heat using natural energy sources, such as the Sun or energy from the ground, as an alternative to burning gas or oil or using electricity. Solar thermal (hot-water) systems A solar thermal hot-water system uses solar radiation to heat water, directly or indirectly. Working principles The key components of a solar thermal hot-water system are: a solar thermal collector a differential temperature controller a circulating pump a hot-water storage cylinder an auxiliary heat source. Solar collector ACTIVITY What would be an auxiliary heat source Differential from the diagram shown temperature To hot taps in Figure 1.2? controller Hot-water storage cylinder Auxiliary heat source Cold water in Circulating pump p Figure 1.2 Solar thermal hot-water system components 4 9781398361607.indb 4 27/07/22 9:38 PM  Chapter 1 Environmental technologies Solar thermal collector A solar thermal collector is designed to collect heat by absorbing heat radiation from the Sun. The energy from the Sun heats the heat-transfer fluid contained in the system. There are two types of solar thermal collector: flat-plate collectors evacuated-tube collectors. Flat-plate collectors are less efficient but cheaper than evacuated-tube collectors. With a flat-plate collector, the heat-transfer fluid circulates through the collectors and is directly heated by the Sun. The collectors need to be well insulated to avoid heat loss. Inlet connection Cover: protecting the absorber plate and preventing loss of heat Outlet connection Collector housing: made from aluminium alloy or galvanised steel – fixes and protects the absorber plate Flow tubes Insulation: to the bottom and sides of Absorber plate: usually black chrome absorbing the collector to reduce the loss of heat coating to maximise heat-collecting efficiency  Figure 1.3 Cutaway diagram of a flat-plate collector Evacuated-tube collectors are more efficient but more expensive than flat-plate collectors. An evacuated-tube collector consists of a specially coated, pressure-resistant, double-walled glass tube. The air is evacuated from the glass tube to aid the transfer of heat from the Sun to a heat tube that is housed within the glass tube. The heat tube contains a temperature-sensitive medium, such as methanol, that, when heated, vaporises. The warmed gas rises within the glass tube. A solar collector will contain several evacuated tubes in contact with a copper header tube that is part of the solar heating circuit. The heat tube is in contact with the header tube. The heat from the methanol vapour in the heat tubes is transferred by conduction to the heat-transfer fluid flowing through the solar heating circuit. This process cools the methanol vapour, which condenses and runs back down to the bottom of the heat tubes, ready for the process to start again. The collector must be mounted at a suitable angle to allow the vapour to rise and the condensed liquid to flow back down the heat tubes. 5 9781398361607_CH01.indd 5 29/07/22 2:05 PM  The City & Guilds Textbook: Electrical Installations Book 2 Heat transfer m to ot Outer tube Solar energy t op to b o absorbed by s t rns r ise retu Selective evacuated tube ur d po ui coating Va d liq se Inner tube en nd Copper header Co Heat absorbed He by heat tube at tr an sf er  Figure 1.4 Evacuated-tube collector Differential temperature controller The differential temperature controller (DTC) has sensors connected to the solar collector (high level) and the hot-water storage system (low level). It monitors the temperatures at the two points. The DTC turns the circulating pump on when there is enough solar energy available and there is a demand for water to be heated. Once the stored water reaches the required temperature, the DTC shuts off the circulating pump. Circulating pump The circulating pump is controlled by the DTC and circulates the system’s heat- transfer fluid around the solar hot-water circuit. The circuit is a closed loop between the solar collector and the hot-water storage tank. The heat-transfer fluid is normally water-based but, depending on the system type, usually also contains antifreeze (glycol) so that at night, or in periods of low temperatures, it does not freeze in the collector. Hot-water storage cylinder The hot-water storage cylinder enables the transfer of heat from the solar collector circuit to the stored water. Several different types of cylinder or cylinder arrangement are possible. Twin-coil cylinder With this type of cylinder, the lower coil is the solar heating circuit and the upper coil is the auxiliary heating circuit. Cold water enters at the base of the cylinder and is heated by the solar heating coil. If the solar heating circuit cannot meet the required demand, then the boiler will provide heat through the upper coil. Hot water is drawn off, by the taps, from the top of the cylinder. 6 9781398361607.indb 6 27/07/22 9:38 PM  Chapter 1 Environmental technologies Solar collector Boiler  Figure 1.5 Twin-coil cylinder Alternatives An alternative arrangement is to use one cylinder as a solar preheat cylinder, the output of which feeds a hot-water cylinder. The auxiliary heating circuit is connected to the second cylinder. Solar collector Boiler  Figure 1.6 Using two separate cylinders The two arrangements that have been described are indirect systems, with the solar heating circuit forming a closed loop. Direct system A direct system is an alternative to an indirect system. In direct systems, the domestic hot water that is stored in the cylinder is directly circulated through the solar collector and is the same water that is drawn off at the taps. Owing to this fact, antifreeze (glycol) cannot be used in the system, so it is important to use freeze-tolerant collectors. Auxiliary heat source In the UK there will be times when there is insufficient solar energy available to provide adequate hot water. On these occasions an auxiliary heat source will be 7 9781398361607.indb 7 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 required. Where the premises have space heating systems installed, the auxiliary heat source is usually this boiler. Where no suitable boiler exists, the auxiliary heat source will be an electric immersion heater. Location and building requirements The following factors should be considered when deciding whether or not a solar thermal hot-water system is suitable for particular premises. The orientation of the solar collectors The optimum direction for the solar collectors to face is due south. However, as the Sun rises in the east and sets in the west, any location with a roof facing east, south or west is suitable for mounting a solar thermal system, although the efficiency of the system will be reduced for any system not facing due south. The tilt of the solar collectors During the year, the maximum elevation or height of the Sun, relative to the horizon, changes. It is lowest in December and highest in June. Ideally, solar collectors should always be perpendicular to the path of the Sun’s rays. As it is generally not practical to change the tilt angle of a solar collector, a compromise angle has to be used. In the UK, the angle is 35°; however, the collectors will work, but less efficiently, from vertical through to horizontal. Shading of the solar collectors Any structure, tree, chimney, aerial or other object that stands between the collector and the Sun will block the Sun’s energy. The Sun shines for a limited time and any reduction in the amount of heat energy reaching the collector will reduce the collector’s ability to provide hot water to meet the demand.  Table 1.2 Degree of shading of solar collectors Shading % of sky blocked by obstacles Reduction in output Heavy > 80% 50% Significant > 60–80% 35% Modest > 20–60% 20% None or very little ≤ 20% No reduction The suitability of the structure for mounting the solar collector The structure has to be assessed as to its suitability for the chosen mounting system. Consideration needs to be given to the strength and condition of the structure and the suitability of fixings. The effect of wind must also be taken into account. The force exerted by the wind on the collectors, an upward force known as ‘wind uplift’, affects both the solar collector fixings and the fixings holding the roof members to the building structure. In the case of roof-mounted systems on blocks of flats and other shared properties, the ownership of the structure on which the proposed system is to be installed must be considered. 8 9781398361607.indb 8 27/07/22 9:38 PM  Chapter 1 Environmental technologies The space needed to mount the collectors is dependent on the demand for hot water. The number of people occupying the premises determines the demand for hot water and, therefore, the number of collectors required, and the space needed to mount them. Compatibility with the existing hot-water system ACTIVITY Solar thermal systems provide stored hot water rather than instantaneous hot Conduct research to water. Premises using under/over-sink water heaters and electric showers will investigate: not be suitable for the installation of a solar thermal hot-water system; neither how much water an will premises using a combination boiler to provide hot water, unless substantial average person uses in changes are made to the hot-water system. one day in the UK how much of this is hot Planning permission water Permitted development applies where a solar thermal hot-water system is how much is returned installed: as waste water. on a dwelling house or block of flats on a building within the grounds of a dwelling house or block of flats as a stand-alone system in the grounds of a dwelling house or block of flats. However, there are criteria to be met in every case. The criteria that must be met for building-mounted systems are that: the solar thermal system cannot protrude more than 200 mm from the wall or the roof slope the solar thermal system cannot protrude past the highest point of the roof (the ridge line), excluding the chimney. The criteria that must be met for stand-alone systems are that: only one stand-alone system is allowed in the grounds the array cannot exceed 4 m in height the array cannot be installed within 5 m of the boundary of the grounds the array cannot exceed 9 m2 in area no dimension of the array can exceed 3 m in length. The criteria that must be met for both stand-alone and building-mounted systems are that: the system cannot be installed in the grounds, or on a building within the grounds, of a listed building or a scheduled monument if the dwelling is in a conservation area or a World Heritage Site, then the array cannot be closer to a highway than the house or block of flats. In every other case, planning permission will be required. Compliance with Building Regulations The Building Regulations applicable to the installation of solar thermal hot-water systems are outlined in Table 1.3. 9 9781398361607.indb 9 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2  Table 1.3 Building Regulations applicable to solar thermal hot-water systems Part Title Relevance A Structure Where equipment and components can put extra load on the structure of the building, or the fabric requires modifications such as chases, suitability of the structure must be considered. B Fire safety Where holes for pipes are made, this may reduce the fire resistance of the building fabric. C Site preparation and resistance Where holes for pipes and fixings for collectors are made, this may reduce the to contaminates and moisture moisture resistance of the building and allow ingress of water. G Sanitation, hot-water safety Hot-water safety and water efficiency must be considered. and water efficiency L Conservation of fuel and power Energy efficiency of the system and the building as a whole must be considered. P Electrical safety The installation of electrical controls and components must be considered. Other regulatory requirements to consider Other regulatory requirements to consider regarding the installation of solar thermal hot-water systems are: BS 7671: 2018 (2022) The IET Wiring Regulations, 18th Edition including amendments Approved Document Part G3: Unvented hot-water storage systems Water Regulations (WRAS). The advantages and disadvantages of solar thermal hot-water systems The advantages of solar thermal hot-water systems are that they: reduce CO2 emissions reduce energy costs are low maintenance improve the energy rating of the building. The disadvantages of solar thermal hot-water systems are that they: may not be compatible with the existing hot-water system may not meet demand for hot water in the winter have high initial installation costs require a linked auxiliary heat source. Heat pumps A water pump moves water from a lower level to a higher level, through the application of energy. Pumping the handle draws water up from a  Figure 1.7 A heat pump moves lower level to a higher level, through the application of kinetic energy. heat from one location to another, just as a water pump As the name suggests, a heat pump moves heat energy from one location to like this one moves water from another, through the application of energy. In most cases, the applied energy one location to another is electrical energy. 10 9781398361607.indb 10 27/07/22 9:38 PM  Chapter 1 Environmental technologies Working principles Heat energy from the Sun exists in the air that surrounds us and in the ground beneath our feet. At absolute zero or 0 K (kelvin), there is no heat in a system. This temperature is equivalent to –273°C so, even with an outside temperature of –10°C, there is a vast amount of free heat energy available. –273 –10 0 20  Figure 1.8 Heat energy exists down to absolute zero (0 K ≈ –273°C) Using a relatively small amount of energy, that stored heat energy in the air or in the ground can be extracted and used in the heating of living accommodation. Heat pumps extract heat from outside and transfer it inside, in much the same way that a refrigerator extracts heat from the inside of the refrigerator and releases it at the back of the refrigerator via the heat-exchange fins. A basic rule of heat transfer is that heat moves from warmer spaces to colder spaces. A heat pump contains a refrigerant. The external air or ground is the medium or heat source that gives up its heat energy. The heat pump operates as follows. When the refrigerant is passed through the Heating system heat source, the refrigerant is cooler than its surroundings and so absorbs heat. The compressor on the heat pump then compresses the refrigerant, causing the gas to heat up. Condenser When the refrigerant is passed to the interior, the refrigerant is now hotter than its surroundings and gives up its heat to the cooler surroundings. Expansion valve The refrigerant is then allowed to expand, which converts it back into a liquid. As the refrigerant expands, it cools, and the cycle starts all over again. The only energy needed to drive the system is the energy required by the compressor. Compressor The greater the difference in temperature between the refrigerant and the heat-source medium from where heat is being extracted, the greater the efficiency of the heat pump. If Evaporator the heat-source medium is very cold, then the refrigerant will need to be colder, to be able to absorb heat, so the harder the compressor must work, and the more energy is needed to Outside air accomplish this.  Figure 1.9 The refrigeration process 11 9781398361607.indb 11 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 Two main types of heat pump are in common use. They are: Heat output 1 kW Electricity input 1 kW ground-source heat pumps ➡ ➡ (GSHPs) 100% effi ciency air-source heat pumps (ASHPs). Heat pumps extract heat energy  Figure 1.10a The efficiency of an electric panel heater from the air or the ground, but the energy extracted is replaced by the action of the Sun. It is not uncommon for heat pumps to have efficiencies in the order of 300%; for an electrical input of 3 kW, a heat output of 9 kW is achievable. If we compare this with other heat appliances (see Figures 1.10 a–c), we Heat output 0.95 kW can see where the savings are made. Gas input 1 kW ➡ ➡ The efficiency of a heat pump is measured in terms of the coefficient of 95% efficiency performance (COP), which is the ratio between the heat delivered and the  Figure 1.10b The efficiency of an A-rated condensing gas boiler power input of the compressor. heat delivered COP = compressor power Electricity input 1 kW The higher the COP value, the greater Heat output 3 kW ➡ ➡ the efficiency. Higher COP values are achieved in mild weather than in cold +2 kW free heat extracted from air equates to a weather because, in cold weather, 300% effi ciency the compressor has to work harder to extract heat. Storing excess heat produced  Figure 1.10c The efficiency of an air-source heat pump Heat pumps are not able to provide instant heat and so therefore work best when run continuously. Stop– INDUSTRY TIP start operations will shorten the lifespan of a heat pump. A buffer tank, simply a large water-storage vessel, is incorporated into the circuit so that, when heat Air-source heat pumps are not just used to warm the inside is not required within the premises, the heat pump can ‘dump’ heat to it and of buildings; they can also thus keep running. When there is a need for heat, this can be drawn from the cool the inside of buildings buffer tank. A buffer tank can be used with both ground-source and air-source during hot days. heat pumps. 12 9781398361607.indb 12 27/07/22 9:38 PM  Chapter 1 Environmental technologies Buffer tank (accumulator) Heat pump To heating system  Figure 1.11 Storing heat in a buffer tank Ground-source heat pumps A ground-source heat pump (GSHP) extracts low-temperature free heat from the ground, upgrades it to a higher temperature and then releases it, where required, for space heating and water heating. Working principles The key components of a GSHP are: heat-collection loops and a pump a heat pump a heating system. The collection of heat from the ground is accomplished by means of pipes that are buried in the ground and contain a mixture of water and antifreeze. This type of system is known as a ‘closed-loop’ system. Three methods of burying the pipes are used. Each method has its advantages and disadvantages. Horizontal loops Piping is installed in horizontal trenches that are generally 1.5–2 m deep. Horizontal loops require more piping than vertical loops – around 200 m of piping for the average house. Ground source to water heat pump with horizontal closed-loop collector Heat pump Building foundations omitted for clarity  Figure 1.12 Horizontal ground loops 13 9781398361607.indb 13 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 Vertical loops Most commercial installations use vertical loops. Holes are bored to a depth of 15–60 m, depending on soil Ground source to water heat pump with vertical conditions, and spaced approximately closed-loop (borehole) 5 m apart. Pipe is then inserted into collector these bore holes. The advantage of this system is that less land is needed. Heat pump Slinkies Building foundations Slinky coils are flattened, overlapping omitted for clarity coils that are spread out and buried, either vertically or horizontally. They Borehole are able to concentrate the area of heat transfer into a small area of land. This reduces the length of trench needing to be excavated and therefore the amount of land required. Slinkies installed in a 10 m long trench will yield around 1 kW of  Figure 1.13 Vertical ground loops heating load. Distribution system Heat exchanger Heat pump  Figure 1.14 Slinkies  Figure 1.15 Slinkies being installed in the ground The water–antifreeze mix is circulated around these ground pipes by means of a pump. The low-grade heat from the ground is passed over a heat exchanger, which transfers the heat from the ground to the refrigerant gas. The refrigerant gas is compressed and passed across a second heat exchanger, where the heat is transferred to a pumped heating loop that feeds either radiators or under-floor heating. 14 9781398361607.indb 14 27/07/22 9:38 PM  Chapter 1 Environmental technologies Heat pump 5.5 bar 17 bar Circulating pump Heating cycle Evaporator Condenser 5.5 bar 17 bar Circulating pump Heat source Earth  Figure 1.16 Ground-source heat pump operating principle Final heat output from the GSHP is at a lower temperature than would be obtained from a gas boiler. The heat output from a GSHP is at 40°C, compared with a gas boiler at 60–80°C. For this reason, under-floor heating, which requires temperatures of 30–35°C, is the most suitable form of heating arrangement to use with a GSHP. Low-temperature or oversized radiators could also be used. A GSHP system, in itself, is unable to heat hot water directly to a suitable temperature. Hot water needs to be stored at a temperature of 60°C. An auxiliary heating device will be necessary in order to reach the required temperatures. A GSHP is unable to provide instant heat and, for maximum efficiency, should run all the time. In some cases, it is beneficial to fit a buffer tank to the output so that any excess heat is stored, ready to be used when required. By reversing the refrigeration process, a GSHP can also be used to provide cooling in the summer. Location and building requirements For a GSHP system to work effectively, and as the output temperature is low, the building must be well insulated. A suitable amount of land has to be available for trenches or, alternatively, land that is suitable for bore holes. In either case, access for machinery will be required. Planning permission The installation of a GSHP is usually considered to be permitted development and will not require a planning application to be made. If the building is a listed building or in a conservation area, the local area planning authority will need to be consulted. 15 9781398361607.indb 15 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 Compliance with Building Regulations The Building Regulations applicable to the installation of GSHPs are outlined in Table 1.4.  Table 1.4 Building Regulations applicable to ground-source heat pumps Part Title Relevance A Structure Where equipment and components can put extra load on the structure of the building, or the fabric requires modification such as chases, suitability of the structure must be considered. B Fire safety Where holes for pipes are made, this may reduce the fire resistance of the building fabric. C Site preparation and resistance Where holes for pipes and fixings for equipment are made, this may reduce the to contaminates and moisture moisture resistance of the building and allow ingress of water. E Resistance to the passage Where holes for pipes are made, this may reduce the soundproof integrity of of sound the building structure. G Sanitation, hot-water safety and Hot-water safety and water efficiency must be considered. water efficiency L Conservation of fuel and power Energy efficiency of the system and the building as a whole must be considered. P Electrical safety The installation of electrical controls and components must be considered. Other regulatory requirements to consider INDUSTRY TIP Other regulatory requirements to consider regarding the installation of GSHPs are: The GOV.UK website provides BS 7671: 2018 (2022) The IET Wiring Regulations, 18th Edition including guidance on the qualifications amendments required to work on equipment F (fluorinated) gas requirements, if working on refrigeration pipework. containing F (fluorinated) gas. Furthermore, you must be qualified in order to work on refrigeration pipework. The advantages and disadvantages of ground-source heat pumps The advantages of GSHPs are that they: are highly efficient are cheaper to run than electric, gas or oil boilers, leading to a reduction in the cost of energy bills reduce CO2 emissions generate no CO2 emissions on site are safe, because no combustion takes place and there is no emission of potentially dangerous gases are low maintenance compared with combustion devices have a long lifespan do not require fuel storage, so less installation space is required can be used to provide cooling in the summer are more efficient than air-source heat pumps. The disadvantages of GSHPs are that: the initial costs are high they require a large area of land 16 9781398361607.indb 16 27/07/22 9:38 PM  Chapter 1 Environmental technologies the design and installation are complex tasks they are unlikely to work efficiently with an existing heating system they use refrigerants, which could be harmful to the environment they are more expensive to install than air-source heat pumps. Air-source heat pumps An air-source heat pump (ASHP) extracts free heat from low-temperature air and releases it, where required, for space heating and water heating. The key components of an ASHP are: a heat pump containing a heat exchanger, a compressor and an expansion valve a heating system. Working principles An ASHP works in a similar way to a refrigerator, but the cooled area becomes the outside world and the area where the heat is released is the inside of a building. The steps involved in the ASHP process are as follows. The pipes of the pump system contain refrigerant that can be a liquid or a gas, depending on the stage of the cycle. The refrigerant, as a gas, flows through a heat exchanger (evaporator), where low-temperature air from outside is drawn across the heat exchanger by means of the unit’s internal fan. The heat from the air warms the refrigerant. Any liquid refrigerant boils to gas. The warmed refrigerant vapour then flows to a compressor. Here, the refrigerant vapour is compressed, causing its temperature to rise further. Following this pressurisation stage, the refrigerant gas passes through another heat exchanger (condenser), where it loses heat to the heating-system water, because it is hotter than the system water. At this stage, some of the refrigerant has condensed to a liquid. The heating system carries heat away to heat the building. The cooled refrigerant passes through an expansion valve, where its pressure drops suddenly and its temperature falls. The refrigerant flows once more to the evaporator heat exchanger, continuing the cycle. Compressor Compression – the gaseous Flow refrigerant is compressed and Outside its temperature increases Heating air system Sudden drop in refrigerant pressure – remaining gas Return Fan cools to liquid Refrigerant liquid is Expansion Gas cools and begins warmed by heat from outside to condense to liquid air and evaporates to gas  Figure 1.17 Air-source heat pump operating principle 17 9781398361607.indb 17 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 There are two types of ASHP in common use. These are: air-to-water pumps air-to-air pumps. An air-to-water pump is the pump described above, and it can be used to provide both space heating and water heating. An air-to-air pump is not suitable for providing water heating. The output temperature of an ASHP will be lower than that of a gas-fired boiler. Ideally, the ASHP should be used in conjunction with an under-floor heating system. Alternatively, it could be used with low-temperature radiators. Location and building requirements The following factors should be considered when deciding whether or not an ASHP is suitable for particular premises. The premises must be well insulated. There must be space to fit the unit on the ground outside the building or to mount it on a wall. There will also need to be clear space around the unit to allow an adequate airflow. The ideal heating system to couple to an ASHP is either under-floor heating or warm-air heating. An ASHP will pay for itself in a shorter period of time if it replaces an electric, coal or oil heating system rather than a gas-fired boiler. Air-source heat pumps are an ideal solution for new-build properties, where high levels of insulation and under-floor heating are to be installed. Planning permission Permitted development applies where an ASHP is installed: on a dwelling house or block of flats on a building within the grounds of a dwelling house or block of flats in the grounds of a dwelling house or block of flats. There are, however, criteria to be met, mainly due to noise generated by the ASHP. The ASHP must comply with the Microgeneration Certification Scheme (MCS) Planning Standards or equivalent. Only one ASHP may be installed on the building or within the grounds of the building. A wind turbine must not be installed on the building or within the grounds of the building. The volume of the outdoor unit’s compressor must not exceed 0.6 m3. The ASHP cannot be installed within 1 m of the boundary. The ASHP cannot be installed on a pitched roof. If the ASHP is installed on a flat roof, it must not be within 1 m of the roof edge. The ASHP cannot be installed on a site designated as a monument. 18 9781398361607.indb 18 27/07/22 9:38 PM  Chapter 1 Environmental technologies The ASHP cannot be installed on a building that is a listed building, or in its grounds. The ASHP cannot be installed on a roof or a wall that fronts a highway, or within a conservation area or World Heritage Site. If the dwelling is in a conservation area or a World Heritage Site, then the ASHP cannot be closer to a highway than the house or block of flats. Compliance with Building Regulations The Building Regulations applicable to the installation of ASHPs are outlined in Table 1.5.  Table 1.5 Building Regulations applicable to air-source heat pumps Part Title Relevance A Structure Where equipment and components can put extra load on the structure of the building, or the fabric requires modification such as chases, the suitability of the structure must be considered. B Fire safety Where holes for pipes are made, this may reduce the fire resistance of the building fabric. C Site preparation and resistance to Where holes for pipes and fixings for equipment are made, this may reduce the contaminates and moisture moisture resistance of the building and allow ingress of water. E Resistance to the passage of sound Where holes for pipes are made, this may reduce the soundproof integrity of the building structure. G Sanitation, hot-water safety and Hot-water safety and water efficiency must be considered. water efficiency L Conservation of fuel and power Energy efficiency of the system and the building as a whole must be considered. P Electrical safety The installation of electrical controls and components must be considered. Other regulatory requirements to consider Other regulatory requirements to consider regarding the installation of ASHPs are: BS 7671: 2018 (2022) The IET Wiring Regulations, 18th Edition including amendments F (fluorinated) gas regulations, if working on refrigeration pipework. The advantages and disadvantages of air-source heat pumps The advantages of ASHPs are that they: are highly efficient are cheaper to run than electric, gas or oil boilers, leading to reductions in the cost of energy bills reduce CO2 emissions generate no CO2 emissions on site are safe, because no combustion takes place and there is no emission of potentially dangerous gases are low maintenance compared with combustion devices do not require fuel storage, so less installation space is required 19 9781398361607.indb 19 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 can be used to provide cooling in the summer are cheaper and easier to install than ground-source heat pumps. The disadvantages of ASHPs are that they: are unlikely to work efficiently with an existing heating system are not as efficient as ground-source heat pumps have high initial costs are less efficient in the winter than in the summer generate noise from the fans have to incorporate a defrost cycle to stop the heat exchanger freezing in the winter. Biomass The major difference between biomass and fossil fuels, both of which are derived from the same source, is time. Fossil fuels, such as gas, oil and coal, have taken millions of years to form. Demand for these fuels is outstripping supply and replenishment. Biomass is derived from recently living organisms. As long KEY TERM as these organisms are replaced by replanting, and demand does not exceed Biomass: The biological replacement time, the whole process is sustainable. Biomass is therefore rightly material from living or regarded as a renewable energy technology. recently living organisms; biomass fuels are usually derived from plant-based material but could be VALUES AND BEHAVIOURS derived from animal Where possible, the use of sustainable fuel sources should be encouraged. material. Fuel pellets Biomass fuel products are much more readily available and significantly can be made from woodworking offcuts, faster to produce, so offer a viable and sustainable alternative to fossil fuel cereals or grain products, consumption. oils, animal fats and However, be mindful of the fact that biomass fuels still produce greenhouse waste fish products. gas emissions, which have a detrimental effect on the environment. Both fossil fuels and biomass fuels are burned to produce heat, and both fuel types release CO2 as part of this process. Carbon dioxide is a greenhouse gas that has been linked to global warming. During their lives, plants and trees absorb CO2 from the atmosphere, to enable growth to take place. When these plants are burned, the CO2 is released once again into the atmosphere. Biomass fuels have two main carbon advantages over fossil fuels. Fossil fuels absorbed CO2 from the atmosphere millions of years ago and have trapped that CO2 ever since. When fossil fuels are burned, they release the CO2 from all those millions of years ago and so add to the present-day atmospheric CO2 level. Biomass absorbs CO2 when it grows, reducing current atmospheric CO2 levels. When biomass is turned into fuel and burned, it releases the CO2 back into the atmosphere. The net result is that there is no overall increase in the amount of CO2 in the atmosphere. 20 9781398361607.indb 20 27/07/22 9:38 PM  Chapter 1 Environmental technologies A disadvantage of biomass is that the material is less dense than fossil fuels, so to achieve the CO2 same heat output, a greater quantity of released to CO2 absorbed biomass than fossil fuel is required. However, atmosphere from atmosphere with careful management, the use of biomass is sustainable, whereas the use of fossil fuels is not. The classes of biomass raw material that can be turned into biomass fuels are: wood Plants and trees crops, such as elephant grass, reed canary Biomass grow, absorbing grass and rapeseed fuel burnt carbon agricultural by-products, such as straw, (photosynthesis) grain husks and forest product waste, and animal waste, such as chicken litter and slurry food waste; it is estimated that some 35% Biomass of food purchased ends up as waste harvested industrial waste. No increase in CO2 Woody biomass  Figure 1.18 The carbon cycle Wood-related products are the primary biomass fuels for domestic use. For wood to work as a sustainable material, the trees used need to be relatively fast growing, so short-rotation coppice woodlands containing willow, hazel and poplar are used on a 3–5-year rotation. Because of this, large logs are not available, neither can slow-growing timbers that would have a higher calorific value be used. Woody biomass as a fuel is generally supplied as: KEY TERM Calorific value: Energy small logs given off by burning. wood chips – mechanically shredded trees, branches, etc. wood pellets – made from sawdust or wood shavings that are compressed to form pellets. The calorific value of woody biomass is generally low. The greener (wetter) the wood is, the lower the calorific value will be. Woody biomass boilers A biomass boiler can be as simple as a log-burner providing heat to a single room or may be a boiler heating a whole house. Woody biomass boilers can be automated so that a constant supply of fuel is available. Wood pellets are transferred to a combustion chamber by means of an auger drive or, if the fuel storage is remote from the boiler, by a suction system. The combustion process is monitored via thermostats in the flue gases, and adjustments are made to the fan speed, which controls air intake, and to the fuel-feed system, to control the feed of pellets. All of this is controlled by a microprocessor. 21 9781398361607.indb 21 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 The hot flue gases are passed across a heat exchanger, where the heat is INDUSTRY TIP transferred to the water in the central-heating system. From this point, the heated water is circulated around a standard central-heating system. In automated biomass boilers, the heat exchangers are self-cleaning and the amount of ash produced is relatively small. As a result, the boilers require little maintenance. The waste gases are taken away from the boiler by the flue and are then dispersed via the flue terminal.  Figure 1.19 Biomass boiler with suction feed system Location and building requirements The following factors should be considered when deciding whether or not a biomass boiler is suitable for particular premises. Space will be required for the storage of the biomass fuel. Easy access will be required for the delivery of the biomass fuel. A biomass boiler may not be permitted in a designated smokeless zone. Smoke-control areas and exempt appliances In the past, when it was common to burn coal as a source of domestic heat or for the commercial generation of heat and power, many cities suffered from very poor air quality. Smogs, which are a mixture of winter fog and smoke, were frequent occurrences. These smogs contained high levels of sulphur dioxide and smoke particles, both of which are harmful to humans. In December 1952, a period of windless conditions prevailed, resulting in a smog in London that lasted for five days. Apart from very poor visibility, it was estimated at the time that this smog contributed to some 4000 premature deaths and another 100 000 people suffered smog-related illnesses. With improved scientific research, it is now suspected that these figures were seriously underestimated and as many as 12 000 people may have died. Not surprisingly, there was a massive public outcry, which led to the government introducing the Clean Air Act 1956 and local authorities declaring areas as ‘smoke-control areas’. The Clean Air Act of 1956 was replaced in 1993. Under this act, it is an offence to sell or burn an unauthorised fuel in a smoke-control area unless it is burned in 22 9781398361607.indb 22 27/07/22 9:38 PM  Chapter 1 Environmental technologies what is known as an ‘exempt appliance’. Exempt appliances are able to burn fuels that would normally be ‘smoky’, without emitting smoke to the atmosphere. Each appliance is designed to burn a specific fuel. Planning permission ACTIVITY Planning permission will not normally be required for the installation of a biomass Use an internet search boiler in a domestic dwelling if the entire work is internal to the building. If the to research the different installation requires an external flue to be installed, it will normally be classed types of biomass fuels that as permitted development, on the condition that the flue is to the rear or side are approved for use in elevation and does not extend more than 1 m above the highest part of the roof. domestic properties. Listed building or buildings in a designated area Check with the local planning authority with regards to both internal work and external flues, because many local authorities will not permit changes to a building’s structure or appearance if the building is listed or in a conservation area. Buildings in a conservation area or in a World Heritage Site Flues should not be fitted on the principal or side elevation if they would be visible from a highway. If the project includes the construction of buildings for the storage of biofuels or to house the boiler, then the same planning requirements as for extensions and garden outbuildings will apply. Compliance with Building Regulations The Building Regulations applicable to biomass fuels are outlined in Table 1.6.  Table 1.6 Building Regulations applicable to biomass fuels Part Title Relevance A Structure Where equipment and components can put extra load on the structure of the building, or the fabric requires modifications such as chases, the suitability of the structure must be considered. B Fire safety Where holes for pipes are made, this may reduce the fire resistance of the building fabric. C Site preparation and resistance to Where holes for pipes and fixings for equipment are made, this may reduce the contaminates and moisture moisture resistance of the building and allow ingress of water. E Resistance to the passage of sound Where holes for pipes are made, this may reduce the soundproof integrity of the building structure. G Sanitation, hot-water safety and Hot-water safety and water efficiency must be considered. water efficiency J Combustion appliances and fuel- Biomass boilers produce heat and therefore must be installed correctly. storage systems L Conservation of fuel and power Energy efficiency of the system and the building as a whole must be considered. P Electrical safety The installation of electrical controls and components must be considered. 23 9781398361607.indb 23 27/07/22 9:38 PM  The City & Guilds Textbook: Electrical Installations Book 2 The advantages and disadvantages of biomass fuels The advantages of biomass fuels are that: they are carbon neutral they are a sustainable fuel source when biomass fuels are burned, the waste gases are low in nitrous oxide, with no sulphur dioxide – both are greenhouse gases. The disadvantages of biomass fuels are that: transportation costs are high; wood pellets or wood chips will need to be delivered in bulk to make delivery costs viable storage space is needed for the fuel; as woody biomass has a low calorific value, a large quantity of fuel will be required consideration must be given as to whether or not adequate storage space is available when a solid fuel is burned, it is not possible to have instant control of heat, as would be the case with a gas boiler; the fuel source cannot be instantly removed to stop combustion they require a suitable flue system. ELECTRICITY-PRODUCING MICRO-RENEWABLE ENERGY TECHNOLOGIES The following electricity-producing micro-renewable energy technologies are KEY TERM discussed in this section: Micro-renewable energy: Small-scale generation of solar photovoltaic energy that is collected micro-wind from renewable resources micro-hydro. which are naturally replenished on a human A major advantage of electricity-producing micro-renewable energy technologies timescale, such as is that they do not use any of the planet’s dwindling fossil fuels. They also do not sunlight, wind, rain, tides, produce any CO2 when in operation. For each of the electricity-producing micro- waves and geothermal renewable energy technologies, two types of connection exist. heat. With an on-grid or grid-tied connection, the system is connected in parallel with the grid-supplied electricity. With an off-grid connection, the system is not connected to the grid but supplies electricity directly to current-using equipment or is used to charge batteries and then supplies electrical equipment via an inverter. The batteries required for off-grid systems need to be deep-cycle type batteries, which are expensive to purchase. The other downside of using batteries to store electricity is that their lifespan may be as short as five years, after which the battery bank will need replacing. With on-grid systems, any excess electricity generated is exported back to the grid. At times when the generation output is not sufficient to meet the demand, electricity is imported from the grid. 24 9781398361607.indb 24 27/07/22 9:38 PM  Chapter 1 Environmental technologies While the following sections will focus primarily on on-grid or grid-tied systems, which are the most common connection types in use, an overview of the components required for off-grid systems is included, to provide a complete explanation of the technology. Demand 2 kW Demand 3 kW Generation 3 kW Generation 2 kW Grid supply 1 kW Grid supply 1 kW exported imported  Figure 1.20a Generation exceeds  Figure 1.20b Demand exceeds demand generation Solar photovoltaic Solar photovoltaic (PV) is the conversion of light into electricity. Light is electromagnetic energy and, in the case of visible light, is electromagnetic energy that is visible to the human eye. The electromagnetic energy released by the Sun consists of a wide spectrum, most of which is not visible to the human eye and cannot be converted into electricity by PV modules. Working principles The basic element of photovoltaic energy production is the PV cell, which is made from semiconductor material. While various semiconductor materials can be used in the making of PV cells, the most common material is silicon. Adding KEY TERMS a small quantity of a different element (an impurity) to the silicon, a process Semiconductor: A known as ‘doping’, produces n-type or p-type semiconductor material. Whether material with resistivity that sits between that it is n-type (negative) or p-type (positive) semiconductor material is dependent of an insulator and a on the element used to dope the silicon. Placing an n-type and a p-type conductor. semiconductor material together creates a p-n junction. This forms the basis of all Photons: Particles of semiconductors used in electronics. energy from the Sun. When photons hit the surface of the PV cell, they are absorbed by the p-type semiconductor material. The additional energy provided by these photons allows electrons to overcome the bon