DE Technologies

Renewable DE

The various renewable DE technologies include: Renewable DE is clean, and provides benefits not only to the individual investor but also to society on a whole. Like DE in general it can provide significant benefits: environmental, economic, efficiency, resource conservation, reliability and security. What makes renewable DE distinct is that renewable DE technologies, as the name suggests, employ sources of energy to make electricity that can be replenished or that do not run-out over time. Sun and wind are perpetual and biomass is another word for fuel that comes from things that grow back including wood waste, agricultural residues etc. Depending on the technology, various processes are at work when renewable DE generates power. It can either be a chemical reaction, as is the case with solar, the movement of wind or water pushing a turbine or heat creating steam to move a turbine as with geothermal or biomass combustion. However, just because a technology is renewable does not mean it can be considered DE. There is a strong argument that to use renewable electricity technologies optimally they should be used in a decentralized application but this is not always the case. Certainly renewable resources naturally occur in a decentralized manner: every year, the sun pours the equivalent of 19 trillion toe of energy onto the earth’s surface a small fraction of which would be sufficient to meet all the world’s energy demand (~9 billion toe per year ) several times over. The energy the sun shines down however is not concentrated- rather spread evenly around the word. The case is similar with other renewable resources such as wind, hydro, geothermal and biomass. Renewable energy, therefore, can be used in DE applications and non DE applications but it is used optimally in DE applications.

Decentralized versus centralized renewables.

Centralized renewables are a move in the right direction but decentralized renewables are the destination. There are several examples of applications where renewable technology cannot be considered DE such “PV farms” or off shore wind farms.

Comparison of decentralized and centralized renewable solar technologies


This small PV panel in the USA shows a typical example of renewable DE because all the power generated from the panel is used locally to pump water for a livestock tank.

Comparison of decentralized and centralized renewable wind technologies

This 100 KW wind turbine at an office building in the US is a good example of DE wind.
Located about 10 kilometers off the coast of Ireland, the Arklow Bank offshore wind park is an example of non DE renewables.

Biomass is a special example of renewable DE because it overlaps also with the other category of DE: cogeneration. In other words biomass (including wood or food scraps, sewage gas, garbage and organic and industrial waste) can be burned for power only (in which case it should not be considered DE) or burned in a cogeneration application creating both useful power and heat. Ideally biomass, like fossil fuels, should always be used in a cogeneration application.

High-Efficiency Cogeneration

High efficiency cogeneration can include fossil fuelled technology or some carbon neutral bio-fuels (gas, liquid or solid). The various DE technologies that can be used in high efficiency cogeneration include:

Cogeneration (otherwise known as combined heat and power) can be defined as the simultaneous production of electricity and useful thermal energy. Large central generators typically convert about a third of the energy in every unit of fuel into energy that is used with the remaining two thirds going up the stack as waste heat. Cogeneration can double this efficiency by making use of the heat produced whenever fuel is burned to produce electricity. By its nature cogeneration must be employed where electricity is required because if waste heat is to be put to use it must be used locally- it is very inefficient to transport waste heat over distances. Waste heat can be used for such purposes as space or water heating, industrial processes that require high temperatures or cooling and refrigeration (in conjunction with an absorption chilller).

The figure below shows how cogeneration improves efficiency and environmental performance by putting normally wasted heat to use. With CHP only 120 units of the initial fuel is wasted to meet energy demand. This is in contrast to separate production of thermal and electrical energy where almost three times as much energy is wasted to meet the same demand. The same principle applies no matter the scale.

Cogeneration applications can be implemented in a wide range of scales from very large installations of several hundred MW- comparable in scale to large central plants, all the way down to the size of a washing machine for use in individual homes. What all these applications have in common is not the size or technology but the fact that they make use of heat that would otherwise have been wasted.

The below photographs illustrate the wide range of scales at which high efficiency cogeneration can offer benefits.

This residential-scale CHP unit, commercially available in Europe, fits nicely under a kitchen counter. It supplies the home space heating hot water and electricity using a sterling engine.
The Conoco Philips Plant in Immingham UK employs a 730MW CHP plant. The facility supplies steam and electricity to the several refineries for industrial processes, and electricity to the National Grid.

Cogeneration applications can employ any number of fuels, from fossil fuels such as natural gas and coal or coal gas to methane from waste water plants or wood chips. Any combustible fuel can be used – some technologies lend themselves better or worse to particular fuels. In the case of fuel cells fuels are not burned but rather reformed to produce energy via a chemical reaction.

Industrial energy recycling and On-site power

There is great potential for utilizing waste streams in industry to generate clean electricity without additional fuel consumption or emissions. The industrial sector accounts for about a third of total global primary energy consumption and much of this energy is unnecessarly wasted.

Industrial energy recycling can be used to turn hot exhaust gases, low-grade fuels (some of which are typically flared) and steam/gas pressure differentials into valuable energy and great savings for the factory owners. Hot exhaust from any process can generate steam that drives turbine generators. Coke ovens, glass furnaces, silicon production, refineries, natural gas pipeline compressors, petrochemical processes, and many processes in the metals industry vent exhaust that can be profitably recycled. The energy potential in pressurized gases also can be profitably turned into electrical energy. Examples of pressurized gas include steam, process exhaust, and compressed natural gas in pipelines. The table below provides an estimation of the amount of electricity that could be generated in the United States if some of the industrial energy recycling potential was realized. Similar potential is realizable in any country where industry is an important part of the economy.

Industrial Recycled Energy Potential in the USA



Annual Potential

Gas compressor stations

16,200 GWh

Flare & stack gas

148,000 GWh

Steam pressure drop

78,000 GWh

Estimated exhaust heat

300,000 GWh

Total potential

492,000 GWh

Source: Recycled Energy Development

The pictures below show two examples of projects making use of energy that otherwise would have been wasted.

This energy recycling plant in the USA captures 1.26 million pounds of steam per hour and 5MW of electric power from industrial waste streams that would otherwise have gone to waste.
This plant in the USA pioneered capturing waste heat from non recovery coke batteries to get energy with zero marginal emissions.