Mitigation – reducing emissions, enhancing sinks

Energy & Transport

Combined Cycle Thermal Power is a technology which combines a gas turbine and a steam generator to produce electricity. Compressed air is mixed with gas which when heated drives a gas turbine. The hot exhaust is captured in a steam generator which drives a steam turbine thus increasing fuel efficiency in the electricity generating process. Reduces GHG emissions considerably compared to coal-fired thermal power.

Large-Scale Combined Heat and Power (CHP) or Cogeneration refers to the technology of capturing waste heat from the steam based electricity production and using it as heating in homes and other places where needed. The technology is routinely used at large scale worldwide e.g. in cities where heating is provided to buildings through extensive underground hot water piping. The technology also has the potential to produce cooling from the waste energy which may be highly relevant in tropical climates. These systems are often referred to as “Trigeneration” or CCHP (Combined Cooling, Heating, and Power). The technology significantly increases fuel efficiency and as such reduces GHG emissions.

Wind Power has in some countries gained high importance as a renewable energy source. Especially off-shore location for large windmill structures (many large mills in a combined grid) is gaining popularity. Major challenges remain in relation to storage and integration of the intermittent energy production into grids, agreeing on feed-in tariffs, and finding adequate locations. As wind resources is highly variable and dependent on local topography, long-term detailed wind measurements are required as part of the feasibility study. Energy storage solutions are typically batteries or a fly-wheel installation. By replacing fossil-fuel based energy production this technology is highly important in reducing GHG emissions. See also the sustainable success story from Samsoe.

Solar Power Photovoltaic (PV) generates electricity directly from the sun’s light and has recently gained high importance as a renewable energy source due to sharply falling prices on photovoltaic solar panels. Photovoltaic solar panels can be used both as small roof-top units for domestic supply, or in large powerplants covering several hectares with solar panels. As for wind energy, the fluctuating power production requires advanced grid integration technologies and/or storage facilities. Current common large-scale storage solutions are batteries, mechanical fly-wheels, and pumping water into high-altitude reservoirs. The technical solutions are constantly evolving. In some countries, feed-in tariffs and energy pricing policies are common obstacles for project implementation. For large-scale solar plants, large land areas must be set aside which may have related negative consequences. See also the sustainable success story from Chile.

Solar Power CSP (Concentrated Solar Power) is using mirrors to reflect and concentrate sunrays towards a receiver that generates steam. The steam is led to a generator producing electricity. The system is thus based on using thermal heat to generate electricity in contrasts to photovoltaic solar power which directly transforms sunlight into electricity. There are two major forms of CSP; parabolic trough and central tower. Parabolic trough systems use rows of trough-shaped mirrors that contrate the solar irradiation on absorber tubes in the focal line of the trough in which a heat-transfer liquid flows. The heat-transfer liquid is led to steam generator where water is converted to super-heated steam which again is led to a turbine which drives a generator. Parabolic trough is the most common CSP technology and is technically and commercially well proven since two decades. An example is the 100MW Shams1 plant in Abu Dhabi, UAE. Central tower systems uses a circle arrangement of mirrors to reflect sunlight at a receiver located in the centre in a high tower. The receiver contains a heat transfer liquid which is used to generate stream as in parabolic trough systems. An example of a central tower system is the 110MW Cerro Dominador plant in Chile. CSP systems have the advantage that the heat transfer liquid (often molten salt) can store the heat for longer time and as such the plant can continue to produce electricity into the night when solar PV systems becomes unproductive. CSP plants require lots of sunlight and large areas to be effective at scale. See also the sustainable success story from Chile.

Small-Scale Hydropower can mean projects up to 30MW but the definition varies between countries. Small hydropower has the advantage of leaving a relatively small footprint on the river flow as not large dams are involved. Smaller headponds, penstock and canals may be used, but the environmental impact is normally negligible compared to large hydropower projects. Being small, construction, and maintenance is also simpler, although maintenance by local communities is often mentioned as major challenge. The production potential may be highly seasonal. Being a renewable energy source, hydropower has large GHG emission reduction potential.

Pumped-storage Hydroelectricity works by storing water at high altitude and producing electricity as a normal hydropower station when required. Water is pumped to the reservoir during period of cheap surplus energy supply, e.g. from wind and solar. The energy stored can be released during periods when alternative energy sources are unavailable. The technology is often considered in relation to load management of grids where intermittent renewable energy sources are connected. The system is a net energy consumer, but has value as temporal energy distribution. Large scale systems require topographically based reservoirs which reduces the feasibility. Smaller systems can use water towers and check dams.

Energy-saving Compact Fluorescent Lamps (CFL) and LED reduces energy consumption for light drastically by replacing incandescent light bulbs. The acquisition price is typically higher, but their much longer lifespan and saved electricity cost largely outweighs this disadvantage. The market for CFL has developed rapidly in recent years, and now also LED lamps with even lower energy consumption are rapidly replacing CFLs. Many governments and electricity companies are sponsoring campaigns to help poorer households make the transition. Reduced energy consumption reduces GHG emissions. See also the sustainable success story on LED lamps from India.

Solar water heater is a simple technology where a solar panel heats water which is stored in isolated tanks for later use. A simple roof-top installation can supply a household with hot water assuming abundant solar radiation is available year-round. Is also commonly used at larger scale with hotels etc. Reduces GHG emissions by saving on energy consumption.

Underground Coal Gasification implies a process where air is pumped into a coal bearing layer and ignited. The combustion creates gasses which are collected for use as energy source. The process eliminates the need for unearthing the coal and in that way may be environmentally more friendly than a traditional coal mine. However, other environmental problems are associated with this process. The energy efficiency may be higher and Co2 emission lower than with normal coal burning. Compared to normal use of coal it may as such reduce GHG emissions although it is still based on fossil-fuels and as such continues to contribute to climate change.

Run-of-River Hydropower  is a type of hydropower plant where water is channelled from the river and into the turbines without creating an artificial heightening of the water surface e.g. through a dam and reservoir construction. Often, the plant will exploit a natural topographical fall in the landscape. The water is released back into the same river the water is taken from. Run-of-River is considered to have less environmental impacts compared to reservoir based hydropower plants, but the term is sometimes used somewhat freely.

Biodigester is a simple installation used to produce biogas from organic waste. Methane is produced by the decomposition of waste by bacteria in an anaerobic environment. The methane can be used as a fuel e.g. in domestic stoves. Biodigesters can take many forms and sizes, but basically is consists of a tank where the waste is deposited, and tubing leading the methane into a collector, often made of flexible material like soft plastic.

The leftover organics waste (digestate) can be used as fertiliser. A biodigester can work on a variety of waste products e.g. animal dung, and effluent from agricultural product processing. The system is highly flexible and can be used on household as well as industrial level. Disadvantage are discomfort from smell, and burning value of gas also depends on type of waste used. The produced gas may replace fossil, wood and other fuels and as such contribute to mitigation.

The “hybrid” HASFC biodigester developed by VACVINA (1998) in North Vietnam. Courtesy www. Mekam.or

ESCO – Energy Services Companies contract is a business arrangement where the energy services company enters a contract with a production company or similar to implement energy saving technologies. The ESCO will gain a percentage of the energy savings, and the production company keeps the rest. Thus, the production company may need only sign a contract in order to making complex significant gains in energy savings. Many forms of ESCO contracts can be negotiated where the ESCO provides all or only part of the required capital need, provides and installs the technology or merely oversee the process and guarantees the quality. When the ESCO raises the capital, the production company avoids burdening its own line of credit. A (or several) reliable investment grade energy audits, performed by the ESCO or a specialised service provider, will be a pre-requisite for the ESCO contract negotiations. A major bottleneck is often to raise the needed capital which can be of considerable size. Banks and other credit institutions are often reluctant to accept collateral in expected future energy savings, and new lending products or guarantee arrangements may need to be developed. The principle of ESCO contracts is not limited to the energy sector, but can be applied to any service which leads to reduction on costs e.g. water saving technology, biogas generation etc. Since the arrangement is profit driven, fixing the enabling conditions may be lead to rapid and autonomous transformations. Energy savings may reduce demand for fossil fuel based energy production and may as such contribute to mitigation.

Bus Rapid Transport System in Jakarta

Bus Rapid Transit (BRT) is a bus-based urban transport system where buses typically uses dedicated lanes separated from the rest of the traffic, combined with bus priority in intersections etc. It is designed to improve capacity and reliability compared to ordinary bus services, and is considered more flexible, simpler, and cheaper than a metro system, but may not be as efficient. Jakarta is a good example from the region where a large BRT has been implemented with varying success (photo below). By making public transportation more efficient, BRT may reduce fossil fuel use and hence contribute to mitigation.

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