Challenges & opportunities in the use of renewable energy

By Eng. B. R. O. Fernando
Past President The Institution of Engineers, Sri Lanka and Consulting Engineer

(This is an extract of a presentation made by Eng. B. R. O.Fernando at Institution of Engineers Sri Lanka and at the British Scholars Association at the British Council recently.)

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, get progressively more difficult. Electricity is not free. It is most expensive and tapped resources are as scarce as they always were.

Climate change and global warming

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 effect of carbon dioxide and other gases in the atmosphere has 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. The source and nature of energy, the security of supply and the equity of distribution, the environmental impacts of its supply and utilisation, are all matters which have to be addressed by suppliers, consumers, governments both rich and poor, industry academia and financial institutions. The discussions held in Kyoto and Johannesburg have increased the awareness of renewable energy. Much effort is still required to make an appreciable impact on the adoption of renewable energy as a major source of energy supply worldwide. Contributions made at various forums look optimistically at renewable energy technologies, both those well established and those that are still a long way from making a commercial impact. 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.

Update on renewable energy

When considering global peace and posterity and the contribution renewable energy can make, the question that we are posed with is whether it is possible for renewable energy to meet all our energy demands globally? Given that four fifths of the world economies come under the designation of "Developing Country", and that they are found in the geographical areas which have an excess of 3000 sunshine hours per year, then by the year 2050 the answer could be Yes.

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. Large hydro schemes are found in South America, Asia and Africa. Geothermal applications are well established not only in Europe but also in North and South America and to a degree in Africa.

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 to generate produces 1110 gm of CO2/kwh; using Gas reduces the figure to 600 g/kwh but using biomass reduces 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 of both Monocrystalline and polycrystalline silicon has increased substantially. Monocrystalline average efficiency is 17.5% and Polycrystalline average efficiency is 15.5% while in the thin film technologies the stability and reliability of amorphous silicon has achieved an average efficiency of 11%.

It is possible to buy a PV system for US$ 5/Wp (Peak Watt.) The UK government allocated US$ 15m to be spent on PV applications within buildings, while the Netherlands, Belgium, Denmark, Germany, USA, Spain and Japan have all created incentive schemes to provide PV usage.

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. Globally, 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$ 5.2bn must be invested immediately and rise to a peak investment of US$ 6.7bn 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.

UK a representative of European Community (EC) Countries with its energy sources being shared by 38.9% from natural gas, 29.1% from coal, 26.5% from nuclear power, 1.5% from oil, renewable and waste 2.8%, miscellaneous 1.2%. However EC has deemed that the percentage of electricity production from the renewables must increase to the proportions specified and achieve the targets by 2010.

Wind energy applications and 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 windfarms and wind turbines and electricity generation costs depend on factors such as location, the size of the machines and size of the windfarm. The growth curve suggests that for every doubling of capacity that the 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 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 minimum price of wind turbines is about e300/sqm. of rotor area. Most wind turbines have ratings around 450 W/sqm of rotor area with a benchmark price of around E670/kW.

Operational Costs fall with the increase in turbine size. The data obtained from German wind installations show that the prices of insurance and guarantees both halve approximately as the ratings increase from 200 to 600 Kw.

Total costs fall from around E25/kW/year at 250 Kw size to around E13/Kw/year at 1500 kW. On Shore "balance of plant" costs typically add 50% to turbine costs bringing the total around US$ 900-1000/Kw.

At Off Shore however additional costs can almost double the turbine costs bringing the total to US$ 1100/Kw upwards. There is a consensus that the installed costs for offshore wind is now in the region of US$1400 to US$ 1600/Kw. The advantages of off shore in many locations is that wind speeds are higher, leading to greater energy productivity. Estimated of installed costs range from US$ 50/Kw which roughly is the lowest cost for on shore, to US$ 1500/Kw in a typical offshore cost For an on shore farm at US$ 1000/Kw, declining from around 9.5US c/kwh at 6.5 m/s to about US 4.5 C/kwh at 9 m/sec.

As the capital costs dominate the calculations, off shore prices at same wind speeds, and US$ 1500/Kw are about 50% higher, and prices on shore, at US$ 750/Kw are about 25% lower. At the high wind speed end these latter prices come within the range of generation costs for a thermal plant

The future

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. Also new technological developments especially in power generation will have the potential to improve the efficiency of energy recovery.

Biomass industries Energy from Waste

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 a fully commercial complex thermo chemical reactors in the form of 100 MWe combined heat and power station. Traditional biomass currently contributes to 12-13% of global primary energy demand, but based mainly in the non-sustainable annual burning of 2x109 t of firewood, 1.3x109 t of crop residue and 1x109 t of 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. CO2output of USA has increased by 20% since 1990 and millions of tons of sulphur in the form of SO2 to SO2 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 provided 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 baseload 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 the disposal 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 landfilled is biologically inactive and dyes 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 plant 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 tons 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. Combined Heat and Power (CHP) is an attractive option when there is a market for the heat. This could be a factory or district heating system for a small community.

ADVANCED THERMAL TECHNOLOGIES.

When the waste stream is of a uniform nature, for example if it has been processed into a homogenous fuel it is more suited to the more "advanced technologies" such as gasification or pyrolisis.

Gasification

Gasification is one of the newer technologies that is increasingly being used for waste disposal. It is a thermo-chemical process in which bio mass is heated in an oxygen deficient atmosphere to produce a low energy gas containing hydrogen, carbon monoxide and methane. The gas can be used as a fuel in a turbine or combustion engine to generate electricity. Gasifiers fuelled by fossil sources such as coal have been operating successfully for many years. But they are now increasingly being developed to accept more mixed fuels, including wastes. New gas clean-up technology ensured that the resulting gas is suitable to be burned in a variety of gas engines with a very favourable emissions profile. Gasifiers operate at a smaller scale than an incineration plant.

Pyrolisis

Pyrolysis is another emerging technology, sharing many of the characteristics of gasification. With gasification, partial oxidation of the waste occurs whilst with pyrolysis the objective is to heat the waste in the complete absence of oxygen. Gas, liquid and char are produced in various quantities. The gas and oil can be processed, stored and transported if necessary and combusted in an engine, gas turbine or boiler. Char can be recovered from the residue and used as a fuel, or the residue passed to a gasifier and the char gasified.

Landfill gas

Energy can also be recovered from waste that had already been landfilled in the form of landfill gas (also referred to as biogas). In a process anaerobic bacteria break down the organic fraction of the landfill in the absence of air, generating a mixture of gases comprising mainly methane and carbondioxide and oxygen, nitrogen and many hundreds of trace compounds and gases as well as water vapour and waste products. The biogas can be collected by drilling wells into the waste and extracting it as it is formed. After cleaning, it can be used in an engine or turbine for power generation, or used to provide heat for industrial purposes situated near the landfill site such as brickworks. Landfill sites can develop commercial quantities of "landfill gas" for up to 30 years after the waste had been deposited. The gas is normally collected from a series of vertical boreholes that have been purpose drilled into the site. I mentioned earlier that methane has a greenhouse gas potential of approximately 21 times that of carbon dioxide and although methane is eventually oxidised in the atmosphere, the uncontrolled release of landfill gas contribute significantly to emissions of greenhouse gas and thus global warming. The International Panel on Climate Change (IPCC) estimated that landfill gas contributed to between 20 million tons and 70 million tons of methane to the atmosphere in 1990. Estimated emissions of methane from solid waste disposal within the 15 European Union countries rose from 7,144,000 tons in 1990 to 7,223,000 tons in 1994 representing the largest single source of methane and around 33% of the total, in the E.U. So removal of methane emissions and conversion to carbon dioxide provides a valuable contribution to the reduction of greenhouse gas emissions. A typical 1 MW landfill gas project will reduce greenhouse gas emissions by around 30,000 tons/year.

ANAEROBIC DIGESTION

The biological processes that take place in a landfill site can be harnessed in a specially designed vessel known as an anaerobic digester to accelerate the decomposition of wastes. Anaerobic digestion is typically used on wet wastes, such as sewage, sludge or animal slurries but the biodegradable fraction of municipal wastes can be added to wetter wastes to increase the biogas output.

SOLAR ELECTRIC POWER

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. Photovolitaic products are proven. But in order to fulfil the technology expectations of this millennium of producing significant portions of the worldelectricity needs it will require phased-up developments in R&O, through manufacturing

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 (PV)

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 4 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 3 years.

The market in UK is still small with only about 3 MW installed. In fact UK’s level of PV power installed per capita is low compared to the other countries like Japan, USA, Switzerland, Germany and Australia which are at the top of the rankings. One could say that we are in the solar age. PV offers much promise as PV generators are silent, clean in operation, highly reliable, low maintenance and extremely robust, with an expected life time of at least 20 to 30 years. They are also very modular and can be adapted for many locations or easily extended.

Market sectors

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. The modules can be assembled in any combination to produce different voltages and power levels.

A tiny unit can power a satellite phone, a large array of modules can generate kilowatts of power for a field hospital or a village.

The third sector is in the use of PV in buildings including those in less sunny climates such as Western and Northern Europe. PV has a huge potential in this sector offering a number of advantages. When integrated into the fabric of the building, it can displace other materials, saving some costs. It needs no extra land and it generates at the point of use, thus reducing transmission losses. When you bring solar power into domestic housing projects, you are literally providing landowners with their own power station right thereon the roof. When used for domestic electricity supply, it will displace purchased electricity and export surplus to the network, as will be evidenced by the meter readings.

The rapid growth of building integrated PV in ‘grid connected distribution’ represents primarily PV in buildings. The installed capacity in 20 reporting countries carried out in a survey is growing rapidly. This survey excludes developing country markets. But there, the emphasis is on rural, off grid, solar home systems which together account for probably less than 100 MW compared to 700 MW included in this survey. Off grid electricity continues to grow significantly in real terms due to international agency funded programmes. However the building integrated PV is the real star in terms of growth.

In theory, if a PV installation replaces the more expensive conventional building materials, it can be shown to be fully economic. In practice this is not generally the case at present, unless there is a considerable incentive available for the installation. Governments that are keen to encourage growth in the PV industry stimulate it by taking the technology a step closer to full commercialisation. This is the stance adopted by the nations which lead the field in per capita installation listed in the survey. Funding for R&D and per capita spending here is also led by these nations with around 50% of the world total originating in Japan.