Services and Utilities Renewable & Low Carbon Technologies An overview
Recommended Reading BSRIA Illustrated Guide to Renewable Technologies.
What do we mean by renewable technologies? Generating electricity Wind turbines, solar photovoltaic (PV) cells, anaerobic digestion. Generating heat (and cooling) Solar thermal panels, heat pumps, Bio-fuels Combined heat and power (CHP) engines do both at the same time Passive technologies like fitting window shades or using natural ventilation are, strictly speaking, not renewable technologies, but they are usually included in building design as part of a holistic approach.
What do we mean by renewable technologies? Renewable technologies may be used at the macro or micro level Macro- generation, e.g. a wind farm generating electricity for the national grid Micro-generation, e.g. PV cells on the roof of a building
Incentives to use renewables at macro level World governments need to act to reduce reliance on fossil fuels EU 2020 targets
EU targets EU 2009 Renewable Energy Directive (RED) sets binding targets for 2020: 20% of EU s energy consumption to come from renewable sources UK s share of this target commits us to consuming 20% of our energy from renewable sources
Incentives to use renewables at micro level Legal Building Regulations Part L London Building Regulations Financial Feed-in tariffs (FITs) Renewable heat incentive (RHIs) The Green Deal Moral incentives Burning fossil fuels like coal, oil and methane gas produces CO 2, which is a greenhouse gas and contributes to global warming Fossil fuels are becoming depleted and will run out Clients sometimes say they can t afford to use renewables how can they afford not to?
April 2010, UK FITs Supposed to encourage small scale, low carbon electricity generation schemes, up to 5MW Support NEW anaerobic digestion, hydro, wind and solar PV schemes A dramatic increase in domestic solar PV is the most obvious result of introduction of FITs
Photovoltaic Tariff lifetimes vary from 10-25 years dependant on technology; PV is 25 years 5-8% return at well sited installations Tariffs decrease in value yearly (incentivising early adoption), but are allocated a tariff when installed, which remains fixed. (See Ofgen website for the latest FIT rates for new installations) Hydro Wind Anaerobic digestion
FIT impact Total installed capacity under FIT scheme to Sept 2010 was 34,558MW Majority of schemes are PV SHARP in N. Wales announced increase in PV production to 500MW / year by Feb 2011 Taking advantage...!
Questions... Is it really as easy as is claimed for the national grid to make use of electricity generated by small consumers? Does the infrastructure actually exist for this to happen? Do FITs really deliver what is claimed? Consumers can feel good about joining the green agenda without high financial cost Some consumers can make a lot of money Economy gets a kick from the growth in PV installation businesses Government favour with the electorate
Wind turbines Wind is a clean source of renewable energy that produces no air or water pollution Some people complain that wind turbines are ugly and/or noisy, the rotating blades can also kill birds and bats (but not nearly as many as cars, power lines, and high-rise buildings do!) For these reasons it is difficult to find sites for wind farms and many are located offshore
Wind turbines Wind turbines are expensive and energy intensive to manufacture critics often say that more CO 2 is produced in the manufacture of a wind turbine than it will ever save over its working life Advances in production techniques are making them cheaper and less energy intensive to manufacture Operational costs are fairly low once a turbine is installed, though there are maintenance and repair costs Planning constraints often make them unsuitable for microgeneration
Wave and tide power o Wave Power: uses the vertical rise and fall of waves to generate electricity via a variety of devices. o Waves, like wind, varies with weather o The problem is securing the devices in the roughest of seas and being able to generate from small waves as well a rough seas
Wave and tide power Tidal Power: uses the diurnal flood and ebb of the tide. Particularly suited to use in estuaries e.g. Seven Estuary. More reliable and predicable than wave and wind power. There are environmental objections to tidal barrages due to loss of habitat etc.
Solar photovoltaics Solar PV cells arranged in panels convert sunlight directly into electricity A system is made up of a series of panels, a DC/AC power converter (or inverter), a racking and mounting system that holds the panels and other components, and electrical interconnections More advanced systems may include battery/charger systems, solar trackers, energy management software etc. A small PV system may provide energy to a single consumer, or to an isolated device like a lamp or a weather instrument Large grid-connected PV systems can provide energy to many consumers The electricity generated can is used directly, fed into the national grid or stored in a battery Typical domestic installation Large scale installation in Germany
Photovoltaic Modules Types of Cell Monocrystalline (single crystalline) 15 to 18% efficiency. Polycrystalline. 13 to 16% efficiency. 1m 2 of photovoltaic array can provide an output of 90 to 110kWh per year. (subject to orientation and tilt angle) Installation can be grid connected or off grid: Grid connected exports excess current back into electrical grid Off-Grid store excess generated current in battery arrays Photovoltaic arrays can be surface mounted (often retrofit) or integrated into the fabric via; Single or flat roof. Building façade Glass Roofs Solar shading devices.
Off-grid PV system Grid connected PV system
Combined heat and power cogeneration The simultaneous generation of useful heat and electrical energy from the same source essentially of a large scale engine or turbine usually fuelled by gas or oil, though biomass may also be utilised The engine is used to turn an electrical generator and so generate power on-site. In large scale installations excess electricity may be sold back to the national grid The waste heat can be used for other processes such as space or water heating An issue that arises in summer months is that heat generated that the building does not require may be wasted Strictly speaking not really a renewable technology but a low carbon technology.
Systems are usually categorised by their electrical output: Micro CHP Mini CHP Small Scale CHP Medium Scale Large Scale less than 5kW 5 to 500kW 500kW to 5MW 5 to 50MW 50+ MW Micro CHP for domestic dwellings use a Stirling Engine where heat expands a gas inside a cylinder. Mini and Small Scale CHP use natural gas or diesel reciprocating engines. Small to large scale CHP tend to use steam or gas turbines.
Tri-Generation CHP CHP system where the waste heat is also used to generate cooling via an Absorption Chiller Absorption chillers are a refrigeration process run by heat rather than a compressor.
Renewable Heat Sources
Renewable Heat Incentive The RHI pays participants of the scheme that generate and use renewable energy to heat their buildings. By increasing the generation of heat from renewable energy sources (instead of fossil fuels), the RHI helps the UK reduce greenhouse gas emissions and meet targets for reducing climate change Since summer 2013 the scheme covers both Domestic and Non-Domestic building. The scheme covers: Solar Thermal Biomass Boilers Ground Source Heat Pumps Air Source heat pumps that heat water.
RHI tariff for Non- Domestic Buildings as of 2013
Solar thermal panels Solar thermal panels are used to generate hot water, usually for domestic purposes. The hot water is stored in a storage cylinder, similar to a normal domestic cylinder only larger and with a second coil. A back-up boiler is usually incorporated for when the sun doesn t shine. eligible for the Renewable Heat Incentive.
Solar Thermal Panels Two types: Flat panel collectors: Lower capital cost but lower output in colder climates Evacuated Tube collectors. Higher output but higher capital cost Both types work best when facing due south with a 35 o slope to the horizontal
Heat Pumps Heat pumps are devices which extract heat from a large volume, external low temperature source, usually the earth (ground source), the outside air (air source) or occasionally a body of water, concentrate it to raise its temperature and then use it to heat either the air inside the building or water (similar to a boiler). They are essentially a refrigeration process working in reverse, taking heat from one place and moving it to another. It is important to realise that the external air or the ground still contain exploitable heat energy, even when they are at extremely low temperatures. Electrical energy is used to drive the process but the heat source is free. Therefore for every 1kW of electrical energy used, approximately 2.3 to 4 kw of heat energy are produced. Most heat pumps currently on the market are reversible, that is, they can be used to either heat or cool the building but a few manufacturers produce heating only heat pumps. Heat pumps are, strictly speaking, not renewable technology, (unless supplied for PV or wind) but they are low carbon technologies because the generate more heat than they consume. Some types of heat pump are currently eligible for the RHI in non-domestic buildings and are likely to become eligible for the RHI for dwellings during 2013.
Heat pumps (ground source)
Heat pumps (ground source) Ground source coils can be horizontal coils which requires large areas or vertical, which require bore-holes. The temperature of the water generated is lower than boilers produce so emitters tend to be larger. Ideal for use with underfloor heating.
Heat pumps (air source) ASHPs operate in a very similar way to GSHPs, except that the low grade heat is drawn from outside air rather than the ground. This removes the necessity for large scale ground excavation and they can therefore often be used as a retro-fit solution.
Biomass & Biofuel Typically Biomass fuel might be: o Energy from biomass is produced by burning organic matter, Biomass products such as trees or crops o Biomass is the solid form of bioenergy, but liquid fuels can also be generated from plant matter and this is referred to as biofuel. o Bioenergy release carbon dioxide when burnt but this is equal to the carbon dioxide was absorbed during the growth of the crops. This makes these fuels carbon neutral. Wood as a by-product of existing forestry and other arboriculture activities sometimes referred to as Virgin Wood Wood (and other crops) grown specifically as a fuel such as short rotation copicing. Reclaimed and waste timber. Biomass can be supplied as logs, chippings, sawdust, pellets & briquettes. o To be truly carbon neutral the biomass material needs to be sources from a local
Biomass Boilers Biomass boilers are similar to solid fuel boilers, they tend to be comparatively large and need storage space for the biomass fuel and a mechanism to automatically stoke the boiler.