Our present consumptive life style is totally unsustainable. For example an average American consumes 350 GJ/year-the highest per capita energy in the world. If every person on this earth has the same wasteful life style as an American then we will require 4 earths to sustain it.

Contrast this with 18 GJ/yr used by an average Indian which is about 5% that of an American. A middle path between U.S. and Indian energy consumption has to be found. I think one can live very decently in about 50-70 GJ per person/yr energy consumption. This amount of energy fueled the life style of Europeans in 1970s which was comfortable and with modern high technologies is achievable. If every citizen of this planet consumes this much energy then earth can support all its inhabitants. Thus for a sustainable India and possibly the world we need to change our life style and at the same time look for alternative sources of energy to sustain it.

Most of the R&D for getting a substitute for oil is based on getting it from biomass which is land based. Thus bio fuels are being produced from crops like corn, sweet sorghum, sugarcane, jatropha etc. Recently research is more focused on using biomass residues via cellulose conversion to ethanol. Since the people who own the cars have money, farming in some parts of the world is being driven to produce fuel rather than food. This is creating serious food shortages and consequent price rise in commodities. Thus use of land to produce bio fuels rather than food has dangerous consequences for the world.

All the life on this planet earth is solar energy based. It produces biomass for our food; produces oil from million years of stored biomass; produces wind and is also responsible for our rain and hence all our water supply. As we advance technologically we will follow this existing evolutionary strategy of life. Thus we will live off sustainably from our energy income (land based solar energy) rather than the capital (fossil fuels or stored solar energy). Use of solar energy together with agricultural residues therefore appears to be the best solution to live sustainably off the land.

All the solar based energies like direct solar or biomass are land or area based. Thus it is useful to have a perspective on their utilization and conversion efficiencies. Also the modern industrial society is electricity based, hence we like to convert all forms of primary energy (like oil, coal, nuclear, solar etc.) into electricity.

Direct conversion of solar energy into electricity either through photovoltaic (PV) cells or through thermal power systems is done at an overall conversion efficiency of 10 to 15% respectively. On the other hand conversion of solar energy to electricity through biomass (either through direct combustion in power plants or through alcohol or biodiesel based engine route) is extremely inefficient with efficiencies ranging from 0.05 to 0.1%. This low efficiency results because the photosynthetic efficiency of converting solar energy into biomass is < 1%. Thus direct conversion of solar into electricity is about 100 to 300 times more efficient than converting biomass into electricity! Consequently the area reduction for energy production by using direct solar energy will be 100-300 times. This is a huge area which can become free for food and chemicals production from biomass ' something that is necessary for long term sustainability of mankind.

It is also interesting to note that solar thermal electricity generation can produce all the electricity (~20,000 MW) that the controversial nuclear deal will help produce from an area of 640 km2 or that of just one taluka. Besides the plants can be set up in couple of years time as opposed to about 10 years or so that a nuclear plant takes to be setup. Also the energy (solar) falls on our country and there is also no problem of disposal of nuclear waste.

Nevertheless conversion of solar energy directly into electricity is presently not cheap since the capital cost is high and also the technology (for solar thermal) is still maturing. Presently there are two methods of producing electricity from solar thermal. In one system parabolic mirrors concentrate solar energy on to a tube which carries high temperature oil. This heats the oil to around 400^oC which in turn produces steam to drive a turbine for electricity generation. In the other system called 'Power Tower' tracking mirrors concentrate solar energy on to a tower where it heats the salt to around 1000^oC which in turn produces steam for turbines. Storage of high temperature oil and salt is still not perfected.

In fact the biggest problem in solar systems is storage of energy when sun is not shinning either during night or in the rainy season. This problem is not there in biomass since the energy is stored in biomass itself. Thus tremendous R&D is needed in battery storage for PV systems and thermal storage for solar thermal conversion systems. Consequently the funding for solar energy thermal systems should match that for biofuels.

In India we are hardly doing anything in the use of solar energy for electricity production via thermal route. Whereas close to 1000 MW is already being generated in U.S. and Europe via this method and the cost of electricity generation is coming down and is quite close to that from coal based power plants.

Similarly agricultural residues available in India can presently produce close to 80,000 MW of electricity or nearly 50% of total installed capacity in the country. Nevertheless for the improvement of land fertility it is necessary that most of these residues should be used as fertilizer. Thus emphasis should be put more on solar thermal electricity.

However all these energy development strategies will become untenable if we follow the U.S. life style and do not put a cap on our greed for materials, resources and energy. Present economic models are based on increased consumption and encourage greed. Ever increasing choices available to an average person fuel the greed impulse since the fear of missing out is very high. Spirituality can help in keeping our greed for materials and resources in check since it helps us become internally secure and hence less greedy.

Spirituality is the state of mind that makes us look deeply into ourselves or the spirit and gives a certain perspective in life. As a person progresses on the path of spirituality his or her priorities in life change. The focus of life shifts more towards getting personal happiness through mental peace and is less on material needs and desires and more towards sustainability. Recent examples of Mahatma Gandhi and Einstein have shown that with very few needs and living very simply they were able to produce the highest quality of thought.

The most important mantra in India is the Gayatri Mantra. It invokes the Sun God and requests him to give us wisdom and enlightenment so that we can live better lives. Use of solar energy to produce electricity via high technology and reducing our greed through spirituality is the best way to live according to its ideal. Indeed a combination of high technology together with spiritual growth will be a new paradigm of sustainable development.