Energi Terbarukan

1. PENDAHULUAN

Kondisi bumi kita kian lama kian mengenaskan karena tercemarnya lingkungan dari efek rumah kaca (greenhouse effect) yang menyebabkan global warming, hujan asam, rusaknya lapisan ozon hingga hilangnya hutan tropis. Semua jenis polusi itu rata-rata akibat dari penggunaan bahan bakar fosil seperti minyak bumi, uranium, plutonium, batu bara dan lainnya yang tiada hentinya.

Padahal kita tahu bahwa bahan bakar dari fosil tidak dapat diperbaharui, tidak seperti bahan bakar non-fosil. Dengan kondisi yang sudah sedemikian memprihatinkan, gerakan hemat energi sudah merupakan keharusan di seluruh dunia. Salah satunya dengan hemat bahan bakar dan menggunakan bahan bakar dari non-fosil yang dapat diperbaharui seperti tenaga angin, tenaga air, energi panas bumi, tenaga matahari, dan lainnya. Duniapun sudah mulai merubah tren produksi dan penggunaan bahan bakarnya, dari bahan bakar fosil beralih ke bahan bakar non-fosil, terutama tenaga surya yang tidak terbatas Sistem Pembangkit Listrik Tenaga Surya akan lebih diminati karena dapat digunakan untuk keperluan apa saja dan di mana saja : bangunan besar, pabrik, perumahan, dan lainnya.

Selain persediaannya tanpa batas, tenaga surya nyaris tanpa dampak buruk terhadap lingkungan dibandingkan bahan bakar lainnya.Di negara-negara industri maju seperti Jepang, Amerika Serikat, dan beberapa negara di Eropa dengan bantuan subsidi dari pemerintah telah diluncurkan program-program untuk memasyarakatkan listrik tenaga surya ini.

Tidak itu saja di negara-negara sedangberkembang seperti India, Mongol promosi pemakaian sumber energi yang dapat diperbaharui ini terus dilakukan. Untuk lebih mengetahui apa itu pembangkit listrik tenaga surya atau kami singkat dengan maka dalam tulisan ini akan dijelaskan secara singkat komponen-komponen yang membentuk sistim kelistrikan tenaga surya dan trend teknologi yang ada.

2. KONSEP KERJA SISTEM PLTS

Pembangkit listrik tenaga surya itu konsepnya sederhana. Yaitu mengubah cahaya matahari menjadi energi listrik. Cahaya matahari merupakan salah satu bentuk energi dari sumber daya alam. Sumber daya alam matahari ini sudah banyak digunakan untuk memasok daya listrik di satelit komunikasi melalui sel surya.

Sel surya ini dapat menghasilkan energi listrik dalam jumlah yang tidak terbatas langsung diambil dari matahari, tanpa ada bagian yang berputar dan tidak memerlukan bahan bakar. Sehingga sel surya sering dikatakan bersih dan ramah lingkungan. Badingkan dengan sebuah generator listrik, ada bagian yang berputar dan memerlukan bahan bakar untuk dapat menghasilkan listrik. Suaranya bising. Selain itu gas buang yang dihasilkan dapat menimbulkan efek gas rumah kaca (green house gas) yang pengaruhnya dapat merusak ekosistem planet bumi kita.

Sistem sel surya yang digunakan di permukaan bumi terdiri dari panel sel surya, rangkaian kontroler pengisian (charge controller), dan aki (batere) 12 volt yang maintenance free. Panel sel surya merupakan modul yang terdiri beberapa sel surya yang digabung dalam hubungkan seri dan paralel tergantung ukuran dan kapasitas yang diperlukan. Yang sering digunakan adalah modul sel surya 20 watt atau 30 watt. Modul sel surya itu menghasilkan energi listrik yang proporsional dengan luas permukaan panel yang terkena sinar matahari.

Rangkaian kontroler pengisian aki dalam sistem sel surya itu merupakan rangkaian elektronik yang mengatur proses pengisian akinya. Kontroler ini dapat mengatur tegangan aki dalam selang tegangan 12 volt plus minus 10 persen. Bila tegangan turun sampai 10,8 volt, maka kontroler akan mengisi aki dengan panel surya sebagai sumber dayanya. Tentu saja proses pengisian itu akan terjadi bila berlangsung pada saat ada cahaya matahari. Jika penurunan tegangan itu terjadi pada malam hari, maka kontroler akan memutus pemasokan energi listrik. Setelah proses pengisian itu berlangsung selama beberapa jam, tegangan aki itu akan naik. Bila tegangan aki itu mencapai 13,2 volt, maka kontroler akan menghentikan proses pengisian aki itu.

Rangkaian kontroler pengisian itu sebenarnya mudah untuk dirakit sendiri. Tapi, biasanya rangkaian kontroler ini sudah tersedia dalam keadaan jadi di pasaran. Memang harga kontroler itu cukup mahal kalau dibeli sebagai unit tersendiri. Kebanyakan sistem sel surya itu hanya dijual dalam bentuk paket lengkap yang siap pakai. Jadi, sistem sel surya dalam bentuk paket lengkap itu jelas lebih murah dibandingkan dengan bila merakit sendiri.

Biasanya panel surya itu letakkan dengan posisi statis menghadap matahari. Padahal bumi itu bergerak mengelilingi matahari. Orbit yang ditempuh bumi berbentuk elip dengan matahari berada di salah satu titik fokusnya. Karena matahari bergerak membentuk sudut selalu berubah, maka dengan posisi panel surya itu yang statis itu tidak akan diperoleh energi listrik yang optimal. Agar dapat terserap secara maksimum, maka sinar matahari itu harus diusahakan selalu jatuh tegak lurus pada permukaan panel surya.

Jadi, untuk mendapatkan energi listrik yang optimal, sistem sel surya itu masih harus dilengkapi pula dengan rangkaian kontroler optional untuk mengatur arah permukaan panel surya agar selalu menghadap matahari sedemikian rupa sehingga sinar mahatari jatuh hampir tegak lurus pada panel suryanya. Kontroler seperti ini dapat dibangun, misalnya, dengan menggunakan mikrokontroler 8031. Kontroler ini tidak sederhana, karena terdiri dari bagian perangkat keras dan bagian perangkat lunak. Biasanya, paket sistem sel surya yang lengkap belum termasuk kontroler untuk menggerakkan panel surya secara otomatis supaya sinar matahari jatuh tegak lurus. Karena itu, kontroler macam ini cukup mahal.

2.1. PHOTOVOLTAIC

Cara kerja sistem Pembangkit Listrik Tenaga Surya dengan

menggunakan Grid-Connected panel sel surya Photovoltaic untuk perumahan :


Modul sel surya Photovoltaic merubah energi surya menjadi arus listrik DC. Arus listrik DC yang dihasilkan ini akan dialirkan melalui suatu inverter (pengatur tenaga) yang merubahnya menjadi arus listrik AC, dan juga dengan otomatis akan mengatur seluruh sistem. Listrik AC akan didistribusikan melalui suatu panel distribusi indoor yang akan mengalirkan listrik sesuai yang dibutuhkan peralatan listrik. Besar dan biaya konsumsi listrik yang dipakai di rumah akan diukur oleh suatu Watt-Hour Meters.

Komponen utama sistem surya fotovoltaik adalah modul yang merupakan unit rakitan beberapa sel surya fotovoltaik. Untuk membuat modul fotovoltaik secara pabrikasi bisa menggunakan teknologi kristal dan thin film. Modul fotovoltaik kristal dapat dibuat dengan teknologi yang relatif sederhana, sedangkan untuk membuat sel fotovoltaik diperlukan teknologi tinggi.

Modul fotovoltaik tersusun dari beberapa sel fotovoltaik yang dihubungkan secara seri dan paralel. Biaya yang dikeluarkan untuk membuat modul sel surya yaitu sebesar 60% dari biaya total. Jadi, jika modul sel surya itu bisa diproduksi di dalam negeri berarti akan bisa menghemat biaya pembangunan PLTS. Untuk itulah, modul pembuatan sel surya di Indonesia tahap pertama adalah membuat bingkai (frame), kemudian membuat laminasi dengan sel-sel yang masih diimpor. Jika permintaan pasar banyak maka pembuatan sel dilakukan di dalam negeri. Hal ini karena teknologi pembuatan sel surya dengan bahan silikon single dan poly cristal secara teoritis sudah dikuasai. Dalam bidang fotovoltaik yang digunakan pada PLTS, Indonesia ternyata telah melewati tahapan penelitian dan pengembangan dan sekarang menuju tahapan pelaksanaan dan instalasi untuk elektrifikasi untuk pedesaan.

Teknologi ini cukup canggih dan keuntungannya adalah harganya murah, bersih, mudah dipasang dan dioperasikan dan mudah dirawat. Sedangkan kendala utama yang dihadapi dalam pengembangan energi surya fotovoltaik adalah investasi awal yang besar dan harga per kWh listrik yang dibangkitkan relatif tinggi, karena memerlukan subsistem yang terdiri atas baterai, unit pengatur dan inverter sesuai dengan kebutuhannya.

Fisika Energi

So what more can be done?

By governments. Most renewable energy technologies have been researched and demonstrated. The need is now for markets, linked with ongoing research and development. Once there is competitive business from expanding demand, financiers, manufacturers and suppliers can make long term plans and prices fall. Governments can control appropriate markets by (i) increasing or decreasing taxation, (ii) awarding grants, (iii) legislating obligations, (iv) changing planning regulations, (v) changing building and manufacturing standards, (vii) transport policy, and (vi) environmental legislation. The potential for markets is learnt from research, which governments should fund in co-operation with industry.

Discussion: What opportunities exist for us to influence government and local authorities about energy developments?

By individuals. Each of us, and our businesses, clubs and churches, can greatly change lifestyle and practice for environmental improvement, especially through our spending and investments. Examples are: insulating homes. contracting with a supplier of green electricity; investing in ethical funds; considering energy use when purchasing white goods, housing, heating plant, lighting, vehicles, travel etc; voting appropriately at elections; studying information; learning from demonstrations of good practice etc. In general it is necessary to quantify and monitor such action so we maintain awareness and responsibility.

Discussion: How should energy criteria affect our individual and group purchases?

By business and industry. Obviously commerce requires continued cash flow, which arises from investment and enterprise, and is sustained by meeting market orders. Nevertheless, commerce should not blindly follow the market from others, but should operate within a code of honourable trade and innovation. This policy has an environmental dimension, which includes its own energy supplies, products and market development. Such enterprise is essential for best technology and implementation, and for best practice and sustainability. Proper utilisation of Renewable Energy is at one with efficiency, low overheads, long-term investment and minimum adverse impacts. The world-wide 20 to 30% per year growth of renewable energy implementation and of energy efficiency procedures are market opportunities that sit well with environmental integrity

Discussion: Where should money be invested and why?

Further sources of information

(best obtained using web search engines with key words)

Books and reports

‘New and renewable energy: prospects in the UK for the 21st Century (supporting evidence)’ DTI and ETSU, March 1999.

‘Renewable Energy’, B. Sørensen, Academic Press, 2000.

‘Renewable Energy Resources’, J. W. Twidell and A. D. Weir, Spon Press/Routledge, revised 2000.

‘Renewable Energy -sources for fuels and electricity’, T. B. Johansson et al (eds), Earthscan, 1993.

Energy: general

UK Dept Trade & Industry (especially electricity). Key official reports and policies, with links to trade associations.

International Energy Agency

Sustainability: general

International Panel on Climate Change

UK Sustainable Development Commission

Royal Commission on Environmental Pollution

Renewable energy

Centre for Alternative Energy

European Forum for Renewable Energy Sources

International Energy Association, renewables

James & James; Renewable Energy World (directories, news, trade)

Canadian: Renewable Energy Technology (’Retscreen’)

International Solar Energy Society (ISES)

UK Dept Environment and Transport (inc. planning, buildings)

UK Dept Trade & Industry: Renewables

Danish wind manufacturers’ association

Credits

This briefing has been prepared for the JRI by Professor John Twidell (Director of the AMSET Centre and Visiting Professor in renewable energy engineering, University of Reading). Thanks are due to Sir John Houghton, Professor Colin Russell, Dr John Sale, Mr Peter Bright, Dr Mike Morecroft, Mr David Thistlethwaite and others within the JRI for their constructive comments.

“Brown Energy” Penghemat BBM 59%, mengapa tidak segera diterapkan?

Setelah beberapa bulan terakhir kita disibukkan dengan berita penemuan “Blue Energy” dari Ngajuk, Jawa Timur, maka hari ini di Harian KOMPAS kita membaca berita tentang sebuah penumuan yang tidak terlalu baru, yaitu “Brown Energy”. Mengapa dipakai kata “Brown”? Sebab penemu awalnya dari teknology ini adalah Mr. Yull Brown dari Australia pada tahun 1974.

Teknologi “Brown Energy” ini sangat sederhana, yaitu dengan menggunakan battery mobil, kita lakukan elektrolisa Air HO) yang dicampur dengan Soda Kue atau Kalium Hidroksida (KOH) guna memperlancar proses itu. Hasilnya adalah gas Hidrogen-Hidrogen-Oxygen (HHO). Has HHO ini kita campur dengan udara untuk dimasukkan ke Piston pembakaran mesin melalui Saringan Udara Karburator.

Hasilnya, mesin mobil bensin maupun mobil diesel bekerja lebih efisien dan bertenaga lebih kuat dibandingkan tanpa campuran gas HHO tersebut. Keuntungan lainnya lagi, hasil pembakaran gas HHO ini lebih ramah lingkungan dari pada aslinya, serta lebih sedikit kerak karbon yang menempel di piston mesin mobil. Efisiensi yang diperoleh bisa mencapai 59%.

Bilamana ini diterapkan diseluruh Indonesia, kita bisa menghemat konsumsi BBM sampai 59%, sehingga memungkinkan Indonesia tidak lagi mengimport BBM. Jadi kita dapat membuat harga BBM tidak lagi terpengaruh oleh fluktuasi harga BBM Luar Negeri yang sampai dengan hari ini sudah mencapai harga US$140/barrel.

Di Indonesia sudah ada tiga orang yang mengembangkan “Brown Energy” ini, yaitu pasangan sdr. Pumpida Hidayatullah dan sdr. Futung Mustari yang memakai Soda Kue sebagai campuran air , serta sdr. Djoko Sutrisno dari Yogyakarta yang memakai Kalium Hidroksida sebagai campuran air.

Sdr. Pumpida Hidayatullah dan Sdr. Futung Mustari telah memberikan presentasi ke KADIN Indonesia. Mereka juga sudah menerbitkan buku “Rahasia Bahan Bakar Air” yang disertai VCD cara membuatnya seharga Rp 40.000,- Biaya untuk perangkat tambahan bagi mesin mobil diperkirakan tidak lebih dari Rp 200.000 -300.000 dan biaya bahan bakunya sangat murah, Rp 30.000 per kg KOH yang dapat dipakai sampai beberapa minggu.

Pertanyaan kami:

1. Apakah Kementrian Negara Ristek sudah meneliti penemuan Penghemat BBM “Brown Enewrgy” ini?

2. Mengapa Pemerintah tidak segera men-sosialisasikan penggunaannya diseluruh Indonesia, agar Indonesia segera terlepas dari Krisis Harga BBM Dunia??

Semoga informasi ini membawa kesejahteraan bangsa dan negara Indonesia yang kita cintai.

Referensi:

1. http://www.brownsgas.com/

2. http://bahanbakarair.com/

3. http://waterbooster.com/

Fisika Energi

Renewable technologies

There are many forms and types of renewables technology; most are now established and with rapidly increasing rates of commercial implementation, often at 30 to 40% growth per year. However, even at these rates, it will be 10 to 20 years before renewables become dominant supplies.

Renewables are classified by immediate source, and then by technology and purpose. The energy is used for heat, machines, electricity generation and transport. The variability of most renewables requires integration and storage, including amalgamation using electricity and heat grids.

The following is an approximate guide for use in the UK, with examples orientated to meaningful household use, either on site or via the purchase of electricity from a ‘Green Electricity’ Supplier.

Benefit in the UK is indicated by the number of
This is only general guidance however, since each place has a distinctive environment and opportunities, e.g. with a suitable stream, hydroelectricity can be the best choice, but few places have this.)

Solar heating

Sunshine for heat (a) absorbed directly e.g. passive solar buildings at zero to 10% extra cost of new-build, and opportunistically for building conversions and extensions; saving 50% of conventional heating, (b) transmitted to use e.g. active solar water heaters using ‘solar thermal panels’ at about £2,000 per house, so reducing conventional water heating by 50% in the UK.

So: consider adding a solar water heater to the cost of your home; let sunshine enter your otherwise insulated house.

Solar electricity

Sunshine generating electricity (a) immediately e.g. photovoltaic solar modules or panels that interconnect with the grid or use battery storage, at £15,000 per house for 50% annual electricity, (b) by machines using heat from ‘solar thermal’ devices e.g. concentrating mirrors raising steam, but not sensible in the UK with cloudy skies.

So: plush buildings can be faced with designer solar panels.

Wind power

This is electricity from wind turbines. The industry is growing rapidly at 30 to 40% per year; each year world-wide there is more new wind power than nuclear or traditional coal power. Wind-electricity costs are less than from nuclear, oil or coal, and about equal to gas, even without considering the abatement benefits of CO2 and other pollution. Controversial impacts are mostly visual and sometimes noise. Most machines are large, perhaps to 100 m in diameter and commercially grid-connected. Siting is both on land and offshore at sea. Small machines, diameter 1 to 10 m, may be used for autonomous electricity supply with batteries, perhaps integrated with other renewables. Capital costs are about £700/kW for large machines, and more for small machines.

So: make a conscious decision about the electricity you buy.

Biomass

This is the generic name for dead and harvested biological matter and its products. There are many opportunities, often complex, for both energy and fertilising nutrients. The use of otherwise waste material, e.g. sewage, gives a cost advantage. Since humans always produce waste, such energy supplies may be considered ‘renewable’. However care is needed to optimise systems and prevent inadvertent pollution. Specific examples are below.

Fire wood

There is a surprising surplus of fallen, waste and scrap wood that can be used dry for domestic, commercial and industrial heating. Purpose-designed stoves and boilers are essential for serious use. Fuel wood and waste is unlikely to be sufficiently ‘smokeless’ in towns and cities. In the country, up to 100% of water and building heat can be supplied, but the supporting effort is significant.

So: if permitted, collect and use firewood efficiently.

Urban waste

On average, at least 5% of a towns energy supply can come from the combustion of local organic wastes, e.g. from ‘rubbish’ collection, industry and agriculture. District heating, combined heat and power, energy efficient buildings and environmental taxes enable such strategies to be successful (as in Denmark and Sweden). However, (i) every opportunity should be taken to recycle actual parts and materials before resorting to combustion, (ii) high quality combustion is needed to minimise pollution.

So: vote for councillors who promote recycling and high-tech use of wastes.

Landfill gas

Purpose built rubbish-pits produce a combustible mix of methane and other gases that may fuel electricity generation at megawatt scale and/or provide commercial process heat. Sewage gas is similar. Likewise Biogas can be collected from animal manure. All such processes support the proper control and treatment of otherwise unhealthy wastes.

So: persuade your sewage company to recover the gas.

Energy crops

Plants may be harvested commercially, dried and then burnt for heat. The heat is used immediately or to generate electricity, hopefully combined with the use of the rejected heat. Partial combustion, in a gasifier, produces a combustible gas to be used as a convenient fuel. High quality equipment minimises smoke emission and ensures optimum combustion. Crop oils, e.g. rape seed, are a basis for transport biofuels at national scale.

So: realise that agriculture provides more than food.

Hydro

Falling water turns a turbine for electricity generation. (a) Large systems have stored water behind dams that inundates valleys, e.g. for 10% of Scotland’s electricity; (b) ‘Run of the river’ systems without storage have less impact, but are small and less continuous, e.g. electricity generation at some old mill sites.

So: balance human impact and conservation.

Wave power

This is electricity from sea waves. The energy travels in large, long-wavelength, Atlantic sea-waves averages about 50 kW/m, and then reduces as the waves become less extreme near to shore. After many years of ongoing research, commercial devices are now operating into the grid and being built in Scotland. Early machines are relatively small (about 150 kW peak electricity), but this capacity will increase with experience.

So: vote for parliamentary candidates favouring research and development of new renewable energy sources.

Geothermal

This is heat from the earth. Hot aquifers, as in Southampton and Paris, may be tapped for district heating, and some for powering turbines for electricity production, as in areas of Italy, New Zealand and California. In principle, but not yet in practice, heat can be extracted from large volumes of granite.

Tidal range

This is hydroelectricity from the rise and fall of tidal height, as water flows through a tidal barrier. About 15% of UK electricity could come from the tidal range power of the Severn Estuary, and lesser amounts from other estuaries with such enhanced tidal range. However the consequent reduction of mud flats, without compensation, would harm wading and migratory birds. Co-operative benefits can be a road across the barrier, flood prevention, enhanced fisheries and leisure facilities.

Tidal flow currents

This is similar to low-head hydro, but commercially not proven. Medium and small scale developments with low impact.

Discussion: What forms of renewable energy could we implement (I) at home, (ii) at work, (iii) in your locality?

Fisika Energi

Added & Edited By:

Eka Kadarisman

Pendidikan Teknik Elektro, Universitas Pendidikan Indonesia

Angga Fuja W.

Department of Physics, Indonesia University of Education

and

Researcher for Tokyo Daigaku

Arip Nurahman

Department of Physics, Indonesia University of Education

and

Follower Open Course at Harvard-MIT Open Course Ware

See also

Energy portal

Wikinews has related news:Renewable energy

Sustainable development portal

Lists

• List of countries by electricity production from renewable source
• List of energy topics
• List of photovoltaics companies
• List of renewable energy organizations
• List of renewable energy topics by country
• List of solar thermal power stations
• List of the largest hydroelectric power stations
• List of wind farms
• List of wind turbine manufacturers

Conservation and efficiency

• Clean Technology Fund
• Directive on Electricity Production from Renewable Energy Sources
• Distributed generation
• Efficient energy use
• Emissions & Generation Resource Integrated Database (eGRID)
• Energy and American Society: Thirteen Myths [book]
• Energy conservation
• Energy security and renewable technology

Resources and sources

• Energy: world resources and consumption
• Eugene Green Energy Standard
• Food, Conservation, and Energy Act of 2008
• Greasestock
• Hybrid power source
• Johannesburg Renewable Energy Coalition

Renewable, alternative, and soft

• Grid energy storage
• International Renewable Energy Agency
• International Renewable Energy Alliance
• International Renewable Energy Conference
• Mitigation of global warming
• Non-renewable energy
• Passive solar building design
• Photovoltaic power stations
• Renewable energy commercialization
• Renewable energy development
• Renewable energy industry
• Renewable energy policy
• Renewable heat
• RenewableEnergyAccess.com
• Small is Profitable
• Soft energy technologies
• Sustainable energy
• Waste-to-energy
• Zero energy building

Phase out of other energies

• Fossil fuels phase out:
  • Coal phase out
  • Petroleum phase-out
• Nuclear phase-out

Fisika Energi

What of nuclear power?

Radioactive materials dispersed within the Earth’s structure, produce sufficient heat to prevent the inner core from cooling; however this important flux of heat is much less than solar heat. The dispersed and buried nature of the material overwhelmingly prevents the radioactivity from affecting organic life. Likewise the relatively small amounts used so beneficially in medicine and instrumentation may be controlled and used safely. However if the radioactive material has a long lifetime (perhaps many thousands of years) and is concentrated, as with a significant fraction of nuclear ores and wastes, biological organisms cannot continue in its presence.

Discarded radioactive material is likely to eventually ‘leak’ into the biosphere, to be absorbed and concentrated into food chains, with the higher forms of life accumulating radioactivity with subsequent danger of genetic harm. There is no known and certain way to safeguard radioactive waste from ultimately entering and harming the biosphere. To date, no form of containment is reliable against ingress of water over the thousands of years needed before the radioactivity becomes negligible.

When extracted, nuclear energy is used only for nuclear weapons and/or centralised electricity generation. Usually, as in the UK, these activities have been associated, so causing concern that weapons proliferation and terrorism may stem from nuclear power. In commercial terms, nuclear generated electricity is expensive and only undertaken with considerable government funding. Nuclear accidents are of major concern.

Nevertheless, a significant advantage of nuclear power is the significant abatement of CO2 and other emissions that might otherwise come from fossil fuels. Continued R&D on the political and technical difficulties and opportunities of nuclear power is justifiable, but only in relation to similar effort on fossil fuel and renewable energy. All such effort should be transparent and open to public scrutiny.

Discussion: What are the benefits and disbenefits of utilising nuclear ores? Have these factors changed over the last 20 years? Who needs to use nuclear power; when and how much?

Brown versus Green energy supply

Therefore it is helpful to make 2 classifications of energy supply

(1) brown energy, derived from the underground sources of nuclear ores and fossil fuels, and

(2) green energy, derived from ongoing energy supplies available in the natural environment.

One view from ecology is that Brown Energy sources are effectively ‘removed pollution’, so such fuels are, ab initio, already concentrated pollution. Clearly there is a duty to process and use such fuels efficiently with the minimum of adverse impacts (as is indeed is increasingly practised and the declared aim of ethical business). Nevertheless, the final emissions remain pollution, which is discharged wholly or in part into the air and water of our immediate environment. In contrast, Green Energy supplies at source are intrinsically non-polluting, since life depends upon them. Most categories of Green Energy technology, as explained below, do not emit pollution. Clearly, as we move from Brown to Green energy, the efficient use of present energy and the minimisation of emitted pollution is vital.

Discussion: Where does the ‘natural environment’ start and stop? Is the human economy part of ‘nature’ or separate from it?

Renewable (Green) energy

Renewable energy is energy supplied from the natural and persistent flows of energy in the immediate environment. Obvious examples are sunshine that heats glasshouses and hydropower that generates electricity. Such technologies are called ‘renewables’ and are, by definition, sustainable. The generally benign ecological and environmental impacts of renewables contrasts with the adverse impacts of Brown Energy. By using Renewable Energy instead of Fossil Fuel Energy, buried carbon remains underground (its use is abated). Using carbon that is already circulating in the ecology of the biosphere, e.g. in plants, does not produce ‘extra carbon’ and so does not threaten long-term harm.

The total energy passing through our environment is enormous and predominantly arrives form the Sun; in one hour as much solar energy arrives as is used by the world economy in one year. In addition there are relatively smaller energy fluxes from tides and geothermal heat.

Sunshine transforms into most of the renewable supplies.

Thus sunshine:

• heats the surface (solar water heaters, cookers, dryers, buildings);
• causes wind (wind turbines and pumps) which in turn causes sea waves (wave energy devices);
• evaporates water giving rainfall (hydropower);
• powers photosynthesis in plants (biomass, biofuels, gasifiers, landfill gas) from light (photovoltaic electricity);
• and, via plants, provides animals with food (hence biogas, sewage gas).

In addition tides (tidal power) and subterranean heat (geothermal power stations, heat pumps) give occasional and locally important energy supply possibilities. There is no shortage of renewable energy; the challenge is to develop, manufacture, and utilise the associated technology.

Left to rot, biomass decays to CO2 with slow heat emission. When burnt as fuel, a similar process occurs, but the heat can be used to substitute for Brown Energy, thus abating fossil CO2 emission. Therefore using sustained biomass for energy does not introduce extra carbon into the Atmosphere, as does the combustion of fossil fuels.

Compared with brown energy, renewables harness mild forms of energy and so the equipment is relatively large and visible. It tends to require expensive capital items, though the energy harnessed is free. The visual impact, in contrast to the ecological impact, can be considered adverse.

The more efficient the renewable energy systems, the smaller the equipment and therefore the cheaper the energy supplied; moreover, the visual impact is reduced. With Brown Energy, both the adverse impacts and the costs are reduced if the systems are efficient. Therefore, energy efficiency is of prime importance for both renewables and non-renewables.

Discussion: What benefits do we have, or have we experienced, from forms of renewable energy?