Challenges and opportunities in the use of renewable energy
By B. R. O. Fernando, past president, Institution of Engineers
When nuclear fission power was first becoming a commercial reality, fossil fuel dominated the electricity generation industry and the budding nuclear power industries basked in the glow of numerous promises and said electricity would be almost free or at the very least, like water then was not worth metering. Water has since become an expensive commodity today, referred to as "White Gold" and is now widely metered. Today, the basic problem of nuclear power of ensuring reliable energy at reasonable cost, both in money and environmental terms, gets progressively difficult. Electricity is not free. It is most expensive and tapped resources are as scarce as they always were.

Growing evidence has convinced most of the scientific community that some degree of climate change is taking place. There is no conclusive proof that indicates whether the cause of the climate change is a small glitch in the sun's output of energy, or whether it is due to the activities of human kind or both. But the media and everyone slip easily into the use of phrases like "greenhouse gases" and "global warming". Greenhouse effects of carbon dioxide and other gases in the atmosphere have doomed the planet Venus to have the hottest planetary surface in the Solar System, which has resulted in a hellish atmosphere both physically and chemically. There are an increasing number of signs that the nature of the Earth's surface is beginning to change. At no time in modern history has energy played a more crucial role in the development and well being of nations than at present.

Much effort is still required to make an appreciable impact on the adoption of renewable energy as a major source of energy supply world wide. Wind power, passive and electronic solar energy and certain new methods in the use of biomass have moved into the normal commercial world. Technologies such as waves, ocean, thermal and tidal energy and the hydrogen economy have not, as yet; but the prospects are still good and the potential benefits are enormous.

Presently solar thermal applications such as water heating, processed heat, crop drying and thermal generation are all well established, and to a lesser extent ceramic making, metal melting and water desalination.

Biomass usage for heat and electricity generation, energy crops and residues, liquid gaseous and solid fuels constitute 5% of total prime energy while the ratio increases to 15% in the developing world. It is worth mentioning that if we compare CO2 emissions from electrical power plants, we find that using coal or oil produces 1110 gm of CO2/kwh; using gas reduces the figure to 600 g/kwh but using biomass reduces it dramatically to 16g/kwh (Ref. World Renewable Energy Congress VII Cologne 2002).

On the photovoltaic front which is perhaps the most publicised use of renewable energy and thanks to space exploration, we find that cell and panel efficiency has increased substantially. The real success story in renewable energy lies in the Wind Energy industry. The cost of electricity produced from wind power has in some European countries fallen as low as 4US cents/kWh which is cheaper than from gas. Europe remains the main market for wind power, followed by USA and India.

lobally, the growth of wind power during 2001 was in excess of 30%. If this growth rate were maintained, Europe would have 22% of its electricity supplied from renewable sources by 2010, and globally by 2020 wind energy will produce 12% of electricity equivalent to 1200 GW. In order to achieve this, US $5.2 billion must be invested immediately and rise to a peak investment of US $6.7 billion by 2020. The present installed cost of wind energy has been reduced to a value of US $675/Kw. Denmark represents one of the most successful suppliers of wind energy utilisation.

Wind energy economics
During the twelve years from 1990 to 2002, World Wind Energy capacity has doubled every three years. Wind Energy capacity in 1990 which was 2000 MW has reached 25,000 MW in 2002. The growth rate accelerated in 2001 by 38%. The representative prices of wind farms and wind turbines and electricity generation costs depend on factors such as location, the size of the machines and size of the wind farm. The growth curve suggests that for every doubling of capacity prices fall by 15%. The steady decrease in costs is due to the move towards larger machines. In 1992 the cheapest machine was rated at 300 Kw. In 1996 it was about 500 Kw and now is around 900 Kw. At present the prices of the largest turbines are dearer than those around the 1 MW mark. Large turbines means taller turbines which mean they intercept stronger winds, and this further enhances the attractions of large machines.

The wind industry has delivered impressive reductions in cost and productivity over the past twenty years. Energy generation prices are now almost on par with those of the fossil fuels. If wind energy capacity continues to double every three years or so, accompanied each time by a 15% reduction in wind turbine production costs, there will be a 30% reduction in prices by 2006.

Forecasting electricity prices from the thermal sources of generation is more difficult, but at worst, generation costs from gas will stay level at about 3 US c/kwh with gas prices offsetting gains from lower plant costs and higher efficiency. At best therefore, wind and gas prices might "Cross Over" around 2005 and at worst around 2009.

Biomass industries
Biomass includes a wide range of chemically stored, solar energy resources, all originating from plant material. Conversion into useful energy services and products can be undertaken using a wide range of technological pathways. Biomass products can vary in scale from simple combustion in domestic open fires to bio fermentation processes for the treatment of organic wastes of a community, to fully commercial complex thermo chemical reactors. Traditional biomass currently contributes to 12-13% of global primary energy demand, but based mainly in the non-sustainable annual burning of firewood, crop residue and animal dung. Removal of this material from the land, robs the soil of recycled nutrients, exposes it to wind erosion, reduces the organic matter content and reduces the soil rooting depth.

There are generic environmental issues relating to the biomass base. The USA has fallen behind much of the world in the use of biomass and other renewable energy forms to produce electricity and steam. Instead the USA has embraced coal for energy production. Currently over 52% of US power is fuelled by coal. CO2 emissions for US coal fired plants are estimated to be 2.3 million tons per year. CO2 output of USA has increased by 20% since 1990 and millions of tons of sulphur in the form of SO2 to SO3 are emitted every year.

Wastes from municipal and industrial services represent an increasingly important fuel source that can be used to produce heat and power. These types of wastes are produced worldwide wherever there are centres of population. Using these wastes as fuels can have important environmental benefits. It can provide a safe and cost effective disposal option for wastes that could otherwise pose significant disposal problems. The use of waste as a fuel helps reduce carbon dioxide emissions through displacement of fossil fuels. Methane is a very potent greenhouse gas, 21 times more damaging than carbon dioxide. Produced by biodegradable waste and residues such as bagasese, ricehusks and sawdust when diverted from landfill and used as a fuel. If landfill gas is collected and used as a fuel (rather than be allowed to escape to the atmosphere, methane emissions are avoided).

Any energy that is recovered from biodegradable waste can be regarded as renewable energy. It comes from plant material (either directly or in the case of animal wastes or paper indirectly). As plants grow they absorb carbon dioxide from the atmosphere. When this biomass material is used as a fuel, the CO2 is returned to the atmosphere in a "carbon neutral" cycle, and the biomass is used to displace fossil fuels. Instead of being left to decompose naturally, it will actually help to limit the emission of CO2 and methane into the air.

There are many ways of combining waste disposal with energy recovery. The UK's landfill gas industry is today one of the most developed in the world. For the last 15 years, landfill gas has allowed UK companies to convert a potential hazard into a source of renewable energy. As the industrialised nations make moves towards reducing emissions to the atmosphere in an effort to stem global warming, landfill gas is fast becoming one of the chief areas of activity for developers, providing, as has been proved in the UK, a low cost, reliable base load with clear environmental benefits. Around 600 MW landfill gas capacity is likely to be commissioned.

Combustion with energy recovery
Waste combustion with energy recovery is an established way to dispose of wastes. It decreases the volume of waste and allows for the recovery of metals and other potentially recyclable fractions. After further treatment, most of the remaining residue can be combined with other materials and used as an aggregate material.

Any residue that is land filled is biologically inactive and does not generate potentially harmful emissions. The heat recovered from these plants can be used to generate electricity or can be used for industrial heat applications. The size of energy from waste plants is designed to meet the waste disposal needs of the community taking into account the potential for waste minimisation and recycling. Plants that generate electricity can typically process between 20,000 and 600,0000 tonnes per year and from this they can generate 1 to 40 MW of electricity. Power is produced from these wastes by using the steam raised in the combustion process to drive a steam turbine to generate electricity.

Solar Electric power has demonstrated its effectiveness and holds exceptional promise for electrical generation throughout the world. Its technology makes it suitable for central station installations of gigawatt proportions as well as smaller, remote electrification applications of the 100 Watt size. Solar is an extremely cost effective way of generating electricity in remote locations.

For industrial services that require small amounts of power or for isolated homes, grid connection is often impossible or far too expensive. Solar is a clean alternative that will dramatically reduce maintenance costs. Photovoltaic products are proven.
The traditional concept of a solar cell is that of a solid state (semiconductor) device which produces useful electricity (direct current and voltage) from the sun's energy via the photovoltaic effect. Various solar modules and designs exist that can be integrated into traditional residential architectural plans. The direct current electricity generated in the solar modules is converted to alternating current (AC) that can be used by most standard appliances. Some new solar modules have built in inverters. Batteries are important if you want to store electricity. But you can eliminate them if you are connected to your local electrical utility power gird as is prevalent in most developed countries.

Solar photo voltaics
Solar PV is a new and exciting technology which should not be confused with solar thermal systems. Thermal systems are used to heat water, whereas solar PV actually generates electricity. PV technologies have significant long-term potential to provide sustainable energy for the world's needs. World PV sales continues to grow at a rate of 20-30% per year and it is estimated that the world production in 2001 nearly reached, the 400 MW mark. Solar Cell module shipments continue to increase 25% to 40% annually. The industry roadmap calls for a 25% annual growth (surpassed over the past four years worldwide) in meeting the expected demands for PV products over the next 20 to 30 years. This rate of growth equates to a doubling of the capacity every three years.

The most established market sector for PV is in the power supply for communications, remote sensing, signalling and research centres, whereas the alternatives may be unattractive for reasons such as the pollution and noise caused by some generators, the difficulty of transporting fuel to an isolated location and maintenance costs.

PV is also widely recognised as a solution to the problem of powering millions of homes and farms in developing countries, where relatively small power supplies are needed to provide lighting, radio and TV, telephones and light industry as well as clinics and schools. The electricity can be used to directly power an appliance such as a pump or refrigerator, or it can be converted to AC to power any conventional electrical appliance. For use at night, the energy can be stored in a battery, or as water stored in a tank or as cold in a refrigerator.

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