Renewable Energy Systems.



The activities cover all major renewable energy sources, such as solar thermal and solar photovoltaic systems, wind, small hydropower energy recovery systems, biogas, biomass from wastes, and other emerging technologies like geothermal energy. Several renewable energy systems and devices are commercially available. Several technologies have been developed and deployed in villages and cities during the last 30 years or so. Solar, hydel, and geothermal are the most attractive propositions.

Point to be noted : The renewable energy programmes should cover the entire gamut of technologies. Electric power generation may not be the sole criteria. Eg., fulfilling one of the most urgent needs – air conditioning – without consuming electricity would be a highly desirable outcome of such a system. Making available such resources as potable water can also be a desired output.

The exploitation of solar energy is an important component of renewable energy sector through both the thermal and photovoltaic routes for a variety of applications for meeting decentralised needs in buildings, educational institutions, hospitals, etc.

Cogeneration is the simultaneous production of power either electrical or mechanical and useful thermal energy from a single fuel source. A cogeneration system is an integration of various components into a total system which provides the electrical and thermal requirements of a specific institutional process. Eg., waste heat recovery from a diesel engine.

Small sized hydropower sources are a low cost, environment friendly and renewable source of energy. Small and mini hydels can provide energy in tall buildings or hilly areas. The appropriate form and manner of doing it depends upon the site’s conditions and its needs.

There are vast possibilities of exploiting geothermal energy in India. The site need not be located near any hot spring. The geothermal energy need not be harnessed for electric power generation only.

This free energy can also be tapped with an earth loop. This technology is used to provide a building with centralised heating and cooling. Geothermal heat pumps (GHPs) utilize average ground temperatures between 40˚and 70˚F using heat pumps to heat and cool buildings using the earth as a heat reservoir.

It uses the earth as a heat source (in the winter) or a heat sink (in the summer). This design takes advantage of the moderate temperatures in the ground to boost efficiency and reduce the operational costs of heating and cooling systems.


Sources of energy are well known. Means to harness those are varied. It is the adaptation of the combination of such sources and the choice of the working substance which hold the key to run the system profitably.

It is also well known that each such source of energy has one characteristic – Intermittency. Both in terms of quality and quantity as per the time of the day & season of the year.

This calls for a stable form of ‘energy storage’ system in the design. Capture of energy produced at one time, and use of the same at a later time. That is, the various energies so obtained be collected and stored. And then it be made available for distribution and consumption in a regulated way that will finally become the rated capacity of the system. Compressed air energy storage (CAES) and pumped-storage hydroelectricity (PSH) are very popular. Batteries are losing out.

The choice of a certain system shall be dictated by site location and the user’s needs. Tall buildings are suitable for hydel and wind installations. [See ]

Geo thermal systems need a number of 20-25 feet deep wells to be dug into the ground depending upon the capacity. They have the potential to make the entire building centrally air conditioned.

Setup costs for regenerative energy systems are indeed higher, and the running costs are low maintenance and supervision expenses mainly. If it is a new building, then the said costs should be clubbed with the cost of the building construction. On an existing building, it will be construed as an add-on, although the entire components become part of the building. The investment is usually recovered in the form of energy savings in 3 to 5 years, or even shorter lengths of time with government tax credits and incentives being taken into account.

A specific case of installation in an educational institution.

The system installation fulfils one primary objective – it makes the unit self reliant in terms of energy and water needs..

Besides, the educationists can see the system as an academic study material. The subject areas covered are – from science and technology to humanities. That is, subjects like science, maths, economics, geography, history, philosophy, commerce, law, finance, etc. are included here. The various course structures can be suitably designed.

Apart from academics, the system can be commercially exploited if the office policy permits. Availability of surplus power allows this. Another form is ‘Technology Transfer’ with or without turn-key services. There remains the scope for growth, improvement and evolution as R&D will remain a continuous phenomenon.

One Regenerative Energy Concept.

Application Area : A High Rise Building

A builder mentions a number of features in his up-coming building project. The most important features which a modern day buyer will look for would be Technology related. These could be —

  • Availability of Electric Power at Rs 3 a unit without any pollution (prevailing market tariff Rs 7 a unit)
  • Availability of clean potable water
  • Optional – Make the building fully or partly centrally Air conditioned.

The builder then has enough ammo to lure the scrupulous buyer. Besides, it sets up an example for others.
Achievable. Doable.
The only need is to tap the vast resources that Nature has provided.
The underlying principle is : “Optimum Utilisation and Regeneration”.
The costs involved are only that during the fabrication and installation. This gets clubbed with the actual cost of the building, and enhances the asset value.
The operating costs are nearly NIL, as no fuel is needed. No consumables, and the equipment has very long life. Only maintenance and supervision will be needed.

Flow of Energy. It is just the interface between human need and what nature can provide. In this regenerative energy concept, the twin property of air is attempted to be used. These properties are pneumatic and the fact that air is consumable.
Air has power. That is, air is capable to do work. Because air is compressible.
Air itself is consumable. Air supports life.
Human need is centred around electric power. A compressed air engine driven alternator does it.
Humans need air for daily consumption; ‘conditioned air’ to be precise. That is zero pollutants, oxygen rich, and favourable temperature, humidity and flow.
All these necessities can be fulfilled by suitably tapping the energy sources available easily. These are solar (photo-voltaic and thermal), wind, hydel and geo thermal. The final output is an hybrid of all such available natural resources.
As per the Laws of thermodynamics, a heat engine works best when there is sufficient difference (T2-T1in the temperatures of the source and sink. Herein lies the significance of the ”sink” shown here with infinite capacity. Attempt is being made to make full use of geothermal and solar thermal energies.
Energy from The Wind. The vertical axis wind turbine can run irrespective of the direction of the incoming wind. It is mounted on the top of the building to receive uninterrupted wind. The shaft axis stays vertical. Through a reduction gear mechanism, high torque can be obtained. This torque is used to run the compressor turbine. Speed although is slow, but the running can be continuous; at times very fast depending upon the prevailing weather – calm or stormy. The energy so obtained is collected and stored to be capitalised later, as and when needed.
Hydel Energy Capture. In any high rise building, water after consumption runs down the height of the building through carefully designed pipes. Overhead water tanks overflow. All such water is passed through a pelton type wheel which in turn runs the air compressor through a reduction gear. In this way, energy is stored in the form of compressed air. It comes from water running down the building. It is indeed a source of energy which, by nature, is largely intermittent throughout the day. Nonetheless, it is a power source which should be tapped by all means. Why not? Further, one is bound to consider rain water harvesting. There is indeed a provision to collect rain water during the season at the top most level of the building. Collect and drain. While draining, let it pass through the pelton wheel and give up some of its potential energy.That stored energy can be regulated and utilised as and when required.
Electricity Generation. It is the traditional 3 ph brushless alternator the capacity being determined by the system requirement. The prime mover is an expansion air turbine, or a piston engine running on compressed air. The speed of it be fixed. Regulation of alternator output may not be needed. The cooling of the alternator is achieved through a tapping of cold air from the output of the expander turbine which is extremely cold. Keeping the alternator cool in this way contributes to its higher efficiency. Iron and copper losses are kept to a minimum. The outgoing hot air is again routed to any of the inlets of the air compressor.