Renewable Technologies and Supply Sources
As public awareness to the benefits of using renewably sources energy grows, Green Energy Consulting have developed their brand as a route to market for SME's to access these benefits more easily.
The Renewable Obligations (RO) the current main mechanism for large-scale generation of renewable electricity. This places the an obligation on licensed suppliers to source a specified and annually increasing proportion of their electricity sales from renewable sources, or pay a penalty. These sources however until now have not been easily accessible, GEC through their continued research and market intelligence have forged long-term consultancy agreements with the suppliers. This intern gives clients the opportunity to procure, tender and contract these sources at exclusive rates and term lengths.
Below is an overview of the main sources to which energy is generated from by suppliers in the UK:
Windmills, wind turbines and wind pumps can be used to produce renewable electricity. Wind power equipment ranges from small water pumps and chargers (used to charge batteries at remote locations) to large multi-megawatt wind turbines arranged in wind farms that supply power to the electricity grid. This equipment has been developed to provide a range of power outputs, from under 100W up to 3MW onshore, and up to 7MW offshore. The overall reliability of wind turbines is high – over 97% availability is standard for modern turbines – and modern machines are designed to have a useful life of about 25 years. Turbines can have fixed or variable speed rotors, can be pitch or stall regulated, or in the case of small turbines can have furling rotor blades. When used for electricity generation, turbines can generate either direct or alternating current. The flexibility of design of individual turbine components means that machines can be matched to areas with high, medium or low average wind speeds, from the Arctic to the Sahara, and from mountain tops to locations out to sea.
Large Scale Onshore/Offshore
Large scale wind generation consists of large turbines grouped together on one site to form a wind farm or wind park, either on- or off-shore. The power from the individual turbines is aggregated at a central point before it is fed through a power line to the point where it connects with the national grid. It usually passes through a transformer at the central point to match the voltage to that of the grid. The central point usually doubles as a command point, where computerised equipment can be installed to allow the remote control of the wind farm. This is particularly important for remote and off-shore wind farms, where adverse weather may prevent access for long periods of time
Hydro power is produced when the kinetic energy of flowing water, is converted into electricity by a turbine connected to an electricity generator. Though the UK generates only about 1.3% (5000GKh) of its electricity from hydro electric schemes, hydroelectricity has proven to be an efficient and reliable technology, as most modern plants have energy conversion efficiencies above 90%. Research estimates the remaining hydro potential in the UK ranges from 850-1550MW, which could contribute significantly to the UK's renewable energy targets. Currently hydroelectricity is covered under the Government's Feed-in Tariff (FITs) scheme as well as the Renewables Obligation (RO). Installations up to 50kW are eligible for the FITs, installations between 50kW and 5MW can choose between FITs or ROCs and installations over 5MW are only eligible for ROCs. Hydropower can be exploited at various different scales.
Large-scale is typically taken to mean more than 20MW of grid-connected generating capacity and is usually associated with a dam and a storage reservoir. There are many large schemes in Scotland, which were built during the 1950's. The potential for identifying new large-scale schemes is now more limited, not only because there are fewer commercially attractive sites still available, but also because of environmental constraints.
Marine renewable energy, comprising wave and tidal energy, is a massive untapped resource in the UK. Europe holds 20% – 30% of global tidal resources, 80% of which is located in and around the coastlines of the UK and France. Estimates suggest that, if fully exploited, wave and tidal power could supply at least 10% of the UK's electricity. If utilised, wave and tidal power has the potential to make significant contribution to the mandatory target set by the EU of 15% renewables contribution to total UK energy consumption by 2020.
The power of the waves is readily visible on nearly every ocean shore in the world. Much research has gone into developing technologies to harness the power of these waves energy and transform it into electricity for domestic and commercial use. These technologies fall broadly into three categories:
Machines which channel waves into constricted chambers. As the waves flow in and out of the chamber, they force air in and out of the chamber. These airflows are in turn channelled through a specialised turbine, which is used to drive a generator. This type of machine is principally designed for use on or near the shore, or for incorporation into breakwaters. Commercially, this kind of machine is the most advanced and is particularly advantageous when incorporated into coastal protection.
Fixed or semi-fixed machines which utilise the pressure differential in the water that occurs at a submerged point as the wave passes over that point. The pressure differential is used by a variety of means to cause a fluid to flow in a circuit, which is then used to drive a turbine and generator.
Machines which utilise their buoyancy to cause movement in a part of the device as it moves up and down in the wave. The movement is used either directly or indirectly to drive a generator.
Tidal Stream Energy
Tidal power can use either conventional or new technology to extract energy from a tidal stream. It is usually deployed in areas where there is a high tidal range. Typically a barrage with turbines is built across an estuary or a bay. As the tide ebbs and rises, it creates a height differential between the inner and outer walls of the barrage. Water can then flow through the turbines and drive generators. Some tidal barrages operate on both the rising and falling tide, but others, particularly estuarine barrages, are designed to operate purely on the falling tide. It is also possible to make use of the tidal flow that occurs between headlands and islands or in and out of estuaries. It is this application that is the focus of much research and development, and new products for this purpose are now being commercialised. These "in-flow" tidal turbines can be arranged singly or in arrays, allowing a range of power outputs to be produced.
Biogas typically refers to the gas that is produced from the natural breakdown of organic matter or organic wastes. Because of its ability to make use of wet wastes and manures it can play an important role in the reduction of greenhouse gases.
Landfill gas is a mixture comprising mainly methane and carbon dioxide, formed when biodegradable wastes break down within a landfill as a result of anaerobic microbiological action. As the UK has traditionally land-filled much of its waste, we are currently exploiting this legacy at many landfills, by capturing landfill gas produced as waste decomposes. The biogas can be collected by drilling wells into the waste and extracting it as it is formed. It can then be used in an engine or turbine for power generation, or used to provide heat for industrial processes situated near the landfill site, such as in brickworks. Landfill sites can generate commercial quantities of landfill gas for up to 30 years after wastes have been deposited. Recovering this gas and using it as a fuel not only ensures the continued safety of the site after land-filling has finished, but also provides a significant long term income from power and/or heat sales.
Sewage gas is biogas produced by the digestion and incineration of sewage sludge from waste water plants. The anaerobic digestion of sewage sludge involves fermenting it in tanks at a temperature between 32 and 36°C for about 25 days. The resulting sewage gas is a mixture of methane, carbon dioxide, nitrogen, hydrogen and hydrogen sulphide. This mixture must then be compressed and purified before it can be transformed into mechanical and thermal energy. It can also power a generator to produce electricity.
Biomass is the term for substances which have grown from animal or vegetable matter. Energy from biomass fuels is renewable and can make significant greenhouse gas emissions savings compared to fossil fuels. Biomass can be used for:
- Heat production
- Power Generation
- Combined heat and power
- Production of other fuels
- Transport Fuels
Wood Wood fuel includes logs, woodchip or pellets. The source can be directly from forestry, residues from processing or discarded materials from other sectors such as construction.
Crops grown for the purpose of use in renewable energy technologies are playing an increasingly important role in sustainable development and agricultural diversification. There are two main energy crops currently used for power generation: short-rotation coppice (SRC) and miscanthus. Other purpose-grown crops are used to produce transport biofuels and can also be used to produce biogas.
Wastes and Residues
The biomass in wastes and residues can also be used for energy, from households or the commercial and industrial sector. This includes municipal waste and that from the commercial and industrial sector.