Sunday, February 12, 2012

Distributed Energy System (DES)

Distributed energy system, is a system that generates power, at the point of usage; unlike the centralized power generation, where power is generated at a remote place, and then distributed to various locations, using power transmission grids. The centralized systems became popular, due to its convenience, to transmit large power, over long distances, under high voltage. However, there are number of disadvantages, in centralized power generation and distribution. Most of these power generation plants are using fossil fuels, like coal, oil and gas, whose efficiency is only about 40%; which means, only about 40% of the heat value, of the fuel used, is converted, into electricity, and the balance is a waste heat, discharged, in the form of greenhouse gases, into the atmosphere. That is why; power plants are the largest emitters of greenhouse gases, in the world. These plants are not only the biggest emitters of greenhouse gases, but also a very inefficient, because, bulk of the fuel, is simply combusted and discharged into the atmosphere. With ever increasing cost of oil and gas, these power plants are ‘white elephants’ that drain the oil and gas resources, in the world, and turn them into greenhouse gases. Such inefficiencies, drive the cost of power high, and also increase the pollution levels. This unabated emission of greenhouse gas has to be curtailed. At this juncture of global warming, and increasing energy cost, Governments and companies, should encourage distributed energy systems. The advantage with distributed energy systems is, when energy is generated onsite, using a fuel, the waste heat can be utilized in a productive way, thus, increasing the power efficiencies from 40% up to 80-85%.This increase in efficiency, will result, is the reduction in the cost of energy. The power savings from distributed energy system varies, from 10% up to 80%.Industries and businesses, who use continuous processes (24x7) and whose energy bill is substantial, are the ideal candidates, for distributed energy systems. It is easier, to adopt distributed energy system, with gaseous fuels, like natural gas and Hydrogen, than with liquid fuels such as diesel or solid fuel such as coal. Distributed energy system can even be installed, using ‘Biogas’, where large quantity of organic waste, or waste water is available, throughout the year, like dairy plants, breweries, municipal sewage systems etc.The power generated in DES system, is invariably, a direct current (DC), which is usually converted into AC (alternate current) using rectifiers, before usage. But, part of this DC load, can be used directly in the form of Dc current, wherever necessary. For example, many consumers are using LED (Light emitting diode) bulbs, for lighting, in order to save energy. In distributed energy system, it is possible to use direct current for these applications because, you can save certain amount of energy in converting DC to AC, and then again AC to DC.In fact, many DC operated appliances can be directly connected to DC power. In addition to the above advantages, the waste heat generated during power generation, can be utilized to generate steam, hot water, chilled water or space airconditioning.For example, if a distributed energy system generates, 500 kw electric power, using natural gas, with an efficiency of 30%, the gas consumption will be about 1666 Kws.The remaining waste heat available is about 1166 Kws, which is equivalent to about 300 TR chilling capacity. This chiller can be used to aircondion an office space. The total efficiency of such system can be as much as 80%.The cost of energy is reduced as much as 60% or more, in some cases. Distributed energy system, is the best and cost effective system, to reduce energy bills as well as to reduce greenhouse emissions, because, in the absence of DES system, the power for air-conditioning has to come from the grid. It is a win situation, for everybody involved. Such system can also be used, with Hydrogen gas. In fact, the heat value of Hydrogen is much higher than any other fuel, such as coal, oil or gas. Hydrogen is the energy of the future that is not only clean but also sustainable.