energi terbarukan: 10 alternatif … 250814


Top 10 Renewable Energy Sources

Listverse Staff May 1, 2009

There are many sources of energy that are renewable and considered to be environmentally friendly and harness natural processes. These sources of energy provide an alternate ‘cleaner’ source of energy, helping to negate the effects of certain forms of pollution. All of these power generation techniques can be described as renewable since they are not depleting any resource to create the energy. While there are many large-scale renewable energy projects and production, renewable technologies are also suited to small off-grid applications, sometimes in rural and remote areas, where energy is often crucial in human development.
10

Tidal Power

Tidal energy can be generated in two ways, tidal stream generators or by barrage generation. The power created though tidal generators is generally more environmentally friendly and causes less impact on established ecosystems. Similar to a wind turbine, many tidal stream generators rotate underwater and is driven by the swiftly moving dense water. Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Historically, tide mills have been used, both in Europe and on the Atlantic coast of the USA. The earliest occurrences date from the Middle Ages, or even from Roman times. Tidal power is the only form of energy which derives directly from the relative motions of the Earth–Moon system, and to a lesser extent from the Earth–Sun system. The tidal forces produced by the Moon and Sun, in combination with Earth’s rotation, are responsible for the generation of the tides. British company Lunar Energy announced that they would be building the world’s first tidal energy farm off the coast of Pembrokshire in Wales. It will be the world’s first deep-sea tidal-energy farm and will provide electricity for 5,000 homes. Eight underwater turbines, each 25 metres long and 15 metres high, are to be installed on the sea bottom off St David’s peninsula. Construction is due to start in the summer of 2008 and the proposed tidal energy turbines, described as “a wind farm under the sea”, should be operational by 2010.

9

Wave Power

Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example for electricity generation, water desalination, or the pumping of water (into reservoirs). Wave energy can be difficult to harness due to the unpredictability of the ocean and wave direction. Wave farms have been created and are in use in Europe, using floating Pelamis Wave Energy converters. Most wave power systems include the use of a floating buoyed device and generate energy through a snaking motion, or by mechanical movement from the waves peaks and troughs. Though often co-mingled, wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave power generation is not currently a widely employed commercial technology although there have been attempts at using it since at least 1890. The world’s first commercial wave farm is based in Portugal, at the Aguçadora Wave Park, which consists of three 750 kilowatt Pelamis devices. In the United States, the Pacific Northwest Generating Cooperative is funding the building of a commercial wave-power park at Reedsport, Oregon. The project will utilize the PowerBuoy technology Ocean Power Technologies which consists of modular, ocean-going buoys. The rising and falling of the waves moves the buoy-like structure creating mechanical energy which is converted into electricity and transmitted to shore over a submerged transmission line. A 40 kW buoy has a diameter of 12 feet (4 m) and is 52 feet (16 m) long, with approximately 13 feet of the unit rising above the ocean surface. Using the three-point mooring system, they are designed to be installed one to five miles (8 km) offshore in water 100 to 200 feet (60 m) deep.
8

Solar Power

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Photovoltaic (PV) Solar power is harnessing the suns energy to produce electricity. One of the fastest growing energy sources, new technologies are developing at a rapid pace. Solar cells are becoming more efficient, transportable and even flexible, allowing for easy installation. PV has mainly been used to power small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. The 1973 oil crisis stimulated a rapid rise in the production of PV during the 1970s and early 1980s. Steadily falling oil prices during the early 1980s, however, led to a reduction in funding for photovoltaic R&D and a discontinuation of the tax credits associated with the Energy Tax Act of 1978. These factors moderated growth to approximately 15% per year from 1984 through 1996. Since the mid-1990s, leadership in the PV sector has shifted from the US to Japan and Germany. Between 1992 and 1994 Japan increased R&D funding, established net metering guidelines, and introduced a subsidy program to encourage the installation of residential PV systems. Solar installations in recent years have also largely begun to expand into residential areas, with governments offering incentive programs to make “green” energy a more economically viable option. In Canada the government offers the RESOP (Renewable Energy Standard Offer Program).
7

Wind Power

Wind power is the conversion of wind energy by wind turbines into a useful form, such as electricity or mechanical energy. Large-scale wind farms are typically connected to the local power transmission network with small turbines used to provide electricity to isolated areas. Residential units are entering production and are are capable of powering large appliances to entire houses depending on the size. Wind farms installed on agricultural land or grazing areas, have one of the lowest environmental impacts of all energy sources. Although wind produces only about 1.5% of worldwide electricity use, it is growing rapidly, having doubled in the three years between 2005 and 2008. In several countries it has achieved relatively high levels of penetration, accounting for approximately 19% of electricity production in Denmark, 11% in Spain and Portugal, and 7% in Germany and the Republic of Ireland in 2008. Wind energy has historically been used directly to propel sailing ships or converted into mechanical energy for pumping water or grinding grain, but the principal application of wind power today is the generation of electricity. As of 2008, Europe leads the world in development of offshore wind power, due to strong wind resources and shallow water in the North Sea and the Baltic Sea, and limitations on suitable locations on land due to dense populations and existing developments. Denmark installed the first offshore wind farms, and for years was the world leader in offshore wind power until the United Kingdom gained the lead in October, 2008. Other large markets for wind power, including the United States and China focused first on developing their on-land wind resources where construction costs are lower (such as in the Great Plains of the U.S., and the similarly wind-swept steppes of Xinjiang and Inner Mongolia in China), but population centers along coastlines in many parts of the world are close to offshore wind resources, which would reduce transmission costs.
6

Hydroelectricity

Hydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste. Small scale hydro or micro-hydro power has been an increasingly popular alternative energy source, especially in remote areas where other power sources are not viable. Small scale hydro power systems can be installed in small rivers or streams with little or no discernible environmental effect or disruption to fish migration. Most small scale hydro power systems make no use of a dam or major water diversion, but rather use water wheels to generate energy. This was approximately 19% of the world’s electricity (up from 16% in 2003), and accounted for over 63% of electricity from renewable sources. While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants, for example. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. The Grand Coulee Dam, long the world’s largest, switched to support Alcoa aluminum in Bellingham, Washington for America’s World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminum power) after the war. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand’s Manapouri Power Station was constructed to supply electricity to the aluminium smelter at Tiwai Point.

5

Radiant Energy

This natural energy can perform the same wonders as ordinary electricity at less than 1% of the cost. It does not behave exactly like electricity, however, which has contributed to the scientific community’s misunderstanding of it. The Methernitha Community in Switzerland currently has 5 or 6 working models of fuelless, self-running devices that tap this energy. Nikola Tesla’s magnifying transmitter, T. Henry Moray’s radiant energy device, Edwin Gray’s EMA motor, and Paul Baumann’s Testatika machine all run on radiant energy. This natural energy form can be gathered directly from the environment or extracted from ordinary electricity by the method called fractionation. One of the earliest wireless telephones to be based on radiant energy was invented by Nikola Tesla. The device used transmitters and receivers whose resonances were tuned to the same frequency, allowing communication between them. In 1916, he recounted an experiment he had done in 1896. He recalled that “Whenever I received the effects of a transmitter, one of the simplest ways [to detect the wireless transmissions] was to apply a magnetic field to currents generated in a conductor, and when I did so, the low frequency gave audible notes.”
4

Geothermal Power

Geothermal energy is a very powerful and efficient way to extract a renewable energy from the earth through natural processes. This can be performed on a small scale to provide heat for a residential unit (a geothermal heat pump), or on a very large scale for energy production through a geothermal power plant. It has been used for space heating and bathing since ancient roman times, but is now better known for generating electricity. Geothermal power is cost effective, reliable, and environmentally friendly, but has previously been geographically limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for direct applications such as home heating. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States. As of 2004, five countries (El Salvador, Kenya, the Philippines, Iceland, and Costa Rica) generate more than 15% of their electricity from geothermal sources. Geothermal power requires no fuel, and is therefore immune to fluctuations in fuel cost, but capital costs tend to be high. Drilling accounts for most of the costs of electrical plants, and exploration of deep resources entails very high financial risks. Geothermal power offers a degree of scalability: a large geothermal plant can power entire cities while smaller power plants can supply rural villages or heat individual homes. Geothermal electricity is generated in 24 countries around the world and a number of potential sites are being developed or evaluated.
3

Biomass

Biomass, as a renewable energy source, refers to living and recently dead biological material that can be used as fuel or for industrial production. In this context, biomass refers to plant matter grown to generate electricity or produce for example trash such as dead trees and branches, yard clippings and wood chips biofuel, and it also includes plant or animal matter used for production of fibers, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, and a variety of tree species, ranging from eucalyptus to oil palm (palm oil). The particular plant used is usually not important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing. The existing commercial biomass power generating industry in the United States produces about 0.5 percent of the U.S. electricity supply. Currently, the New Hope Power Partnership is the largest biomass power plant in North America. The facility reduces dependence on oil by more than one million barrels per year, and by recycling sugar cane and wood waste, preserves landfill space in urban communities in Florida.
2

Compressed Natural Gas

Compressed Natural Gas (CNG) is a fossil fuel substitute for gasoline, diesel, or propane fuel. Although its combustion does produce greenhouse gases, it is a more environmentally clean alternative to those fuels, and it is much safer than other fuels in the event of a spill (natural gas is lighter than air, and disperses quickly when released). CNG is used in traditional gasoline internal combustion engine cars that have been converted into bi-fuel vehicles (gasoline/CNG). Natural gas vehicles are increasingly used in Europe and South America due to rising gasoline prices. In response to high fuel prices and environmental concerns, CNG is starting to be used also in light-duty passenger vehicles and pickup trucks, medium-duty delivery trucks, transit and school buses, and trains. Italy currently has the largest number of CNG vehicles in Europe and is the 4th country in the world for number of CNG-powered vehicles in circulation. Canada is a large producer of natural gas, so it follows that CNG is used in Canada as an economical motor fuel. Canadian industry has developed CNG-fueled truck and bus engines, CNG-fueled transit buses, and light trucks and taxis. Both CNG and propane refueling stations are not difficult to find in major centers. During the 1970s and 1980s, CNG was commonly used in New Zealand in the wake of the oil crises, but fell into decline after petrol prices receded.
1

Nuclear Power

Nuclear power is any nuclear technology designed to extract usable energy from atomic nuclei via controlled nuclear reactions. The only method in use today is through nuclear fission, though other methods might one day include nuclear fusion and radioactive decay. All utility-scale reactors heat water to produce steam, which is then converted into mechanical work for the purpose of generating electricity or propulsion. In 2007, 14% of the world’s electricity came from nuclear power, with the U.S., France, and Japan together accounting for 56.5% of nuclear generated electricity. There are 439 nuclear power reactors in operation in the world, operating in 31 countries. According to the World Nuclear Association, globally during the 1980s one new nuclear reactor started up every 17 days on average, and by the year 2015 this rate could increase to one every 5 days. According to a 2007 story broadcast on 60 Minutes, nuclear power gives France the cleanest air of any industrialized country, and the cheapest electricity in all of Europe. France reprocesses its nuclear waste to reduce its mass and make more energy. Reprocessing can potentially recover up to 95% of the remaining uranium and plutonium in spent nuclear fuel, putting it into new mixed oxide fuel. This produces a reduction in long term radioactivity within the remaining waste, since this is largely short-lived fission products, and reduces its volume by over 90%. France is generally cited as the most successful reprocessor, but it presently only recycles 28% (by mass) of the yearly fuel use, 7% within France and another 21% in Russia.

Proponents of nuclear energy contend that nuclear power is a sustainable energy source that reduces carbon emissions and increases energy security by decreasing dependence on foreign oil. Proponents also emphasize that the risks of storing waste are small and can be further reduced by using the latest technology in newer reactors, and the operational safety record in the Western World is excellent when compared to the other major kinds of power plants. Critics believe that nuclear power is a potentially dangerous energy source, with decreasing proportion of nuclear energy in power production, and dispute whether the risks can be reduced through new technology. Proponents advance the notion that nuclear power produces virtually no air pollution, in contrast to the chief viable alternative of fossil fuel. Proponents also point out that nuclear power is the only viable course to achieve energy independence for most Western countries. Critics point to the issue of storing radioactive waste, the history of and continuing potential for radioactive contamination by accident or sabotage, the history of and continuing possibility of nuclear proliferation and the disadvantages of centralized electricity production.

This article is licensed under the GFDL because it contains quotations from Wikipedia.
Listverse Staff

Listverse is a place for explorers. Together we seek out the most fascinating and rare gems of human knowledge. Three or more fact-packed lists daily.

What renewable energy source, if any, has the most promise for becoming a major energy source? The Wall Street Journal put this question to The Experts, an exclusive group of industry and thought leaders who engage in in-depth online discussions of topics from the print Report. This question relates to articles in a recent report which covered topics such as nuclear energy, oil and fracking and formed the basis of a discussion in The Experts stream on Monday, April 15.

The Experts will discuss topics raised in this month’s Big Issues: Energy Report and other Wall Street Journal Reports. Find the energy Experts online at WSJ.com/EnergyReport.

Carl Wiens

Also be sure to watch three energy thought leaders— Ed Begley Jr. (@edbegleyjr), Margaret Walls of Resources for the Future and Kateri Callahan of the Alliance to Save Energy—speak about living, working and playing more sustainably in a live video chat that aired on April 15 at 3 p.m. EDT.
Craig Pirrong : Nothing Beats Natural Gas

To put it provocatively, this question is a request to handicap a race of the lame. All renewables are cursed with fundamental problems that make their future stand-alone (i.e. unsubsidized) viability as anything but a marginal energy source highly questionable.

With respect to electricity generation, the major renewables (wind and solar) are both intermittent and diffuse. These are obstacles inherent in the source of the energy that will be difficult to surmount. One illustration. Here in Texas, when it gets hot—and the demand for electricity spikes—the wind stops blowing. Given the fact that we need generation most when it is hot, this is a serious deficiency. Solar has greater potential, given the prospects for innovations that improve the efficiency of solar panels and reduce the cost of producing them. But even for solar, the vicissitudes of the sun (which vary by season and location) and the diffusive nature of solar power limit its potential.

What’s more, the revolution in natural gas undermines the economics of these technologies.

Countries that have been quite aggressive in their pursuit of wind and solar have realized that their aspirations greatly outpaced the technology. Both Germany and Spain have announced that they will substantially curtail their government support for wind and solar.

With respect to transportation fuels, the outlook is even more problematic. Battery technology has proved a major constraint on the ability to turn electricity (including electricity generated from renewable sources) into an efficient transportation fuel. Ethanol produced from food crops is an economic monstrosity that would require far more space than available here to spell out in proper detail. Ethanol produced from nonfood sources (e.g., non-celluosic ethanol) does not suffer from some of the worst aspects of ethanol derived from corn, say, but has proved stubbornly resistant to commercially economic production. The idea for producing ethanol from wood dates from 1898. It was commercially uneconomical then. It is commercially uneconomical now. It will remain commercially uneconomical for the foreseeable future. That said, it is a technology that has more attractions than the alternatives.

And again, the potential for natural gas as a transportation fuel, and the revolution in natural-gas production, undermine the economics of renewable motor fuels.

Insofar as renewables have desirable environmental attributes (and some—notably corn-based ethanol—may not), the preferable approach is to price these attributes and let the market choose the technologies that produce the best balance between environmental and non-environmental considerations.

Craig Pirrong (@streetwiseprof) is professor of finance and energy markets director for the Global Energy Management Institute at the Bauer College of Business at University of Houston. He was previously Watson family professor of commodity and financial risk management at Oklahoma State University and a faculty member at University of Michigan, University of Chicago and Washington University.
Robert Rapier : My Money Is on Solar PV

Two renewable energy sources are already major energy sources. Hydropower currently provides about 16% of the world’s electricity, which is greater than the percentage produced by nuclear power, and a far greater share than all other renewables combined. In fact, the largest power plant by capacity in the world, as well as four of the five largest power plants in the world are hydroelectric plants. However, most of the world’s best sites for hydropower have already been developed, so global growth in new hydropower capacity is forecast to be slow.

The second major source of renewable energy is traditional biomass, which accounts for two-thirds of the renewable energy in the world. In developing countries, the overwhelming majority of the energy consumed is provided by fuel wood (often unsustainably sourced), which is generally the cheapest fuel option available. Fuel wood is the main energy source for cooking for most of the developing world, and is the primary source of energy for over 2 billion people.

Solar and wind power have both experienced explosive growth over the past decade, but both still account for a very small portion of the world’s energy. Global wind power capacity grew from under 5 gigawatts (GW) in 1996 to nearly 240 GW by 2011—a nearly 50-fold increase. But that translated into only 2.8% of the electricity produced in the U.S. and 1.6% of the electricity produced in China.

Likewise, since 2010 solar photovoltaic (PV) capacity has been added in more than 100 countries, and the estimated global capacity at the end of 2011 was 70 GW—a tenfold increase over the previous five years. But this resulted in only 0.5% of the global electricity demand in 2011.

Solar heating—consisting of solar water heating, space heating for homes and industrial process heat—is often overlooked in discussions of renewable energy. However, global capacity of solar heating applications is far larger than that of solar PV. According to the REN21 Renewables Global Status Report, at the end of 2011 total global capacity of solar hot water and space heating was 232 gigawatts of thermal energy (GWth) (including a solar water heater on my own roof in Hawaii).

So there are some very-fast-growing renewable energy options, and there are also some that are well-established. But if I had to put my money on one option that will likely command a much larger share of energy production in the future, it would be solar PV.

Robert Rapier (@RRapier) is chief technology officer and executive vice president at Merica International, a forestry and renewable energy company. He serves as managing editor for Energy Trends Insider and is chief energy strategist at Investing Daily.
Iván Martén: Expect a Healthy Mix of Renewables

Several renewable-energy sources are technologically mature. Several already are making a significant contribution to energy generation, such as hydropower in Brazil, biomass in Finland, onshore wind in Denmark, solar photovoltaic in Germany or geothermal energy in Indonesia. Apart from hydropower, this strong footprint so far has largely been accomplished through strong regulatory support. Future growth of renewable energy will increasingly be driven by cost competitiveness with fossil-fuel based generation: The cost of renewables will continue to decline while the cost of fossil fuels is expected to increase further. Today, solar and wind have already reached this point in several countries that have abundant resources and high cost of electricity.

Moreover, an increasing share of fluctuating solar and wind energy will drive higher demand for flexible and dispatchable “green energy” sources. If electricity storage becomes cheap, as expected, that could be a true game changer.

In general, adoption of a diversified mix of different renewable energy sources including storage will benefit power quality and overall security of supply.

Looking at the global picture, therefore, I do not believe there will be one winning renewable technology. Rather, there will be a healthy mix that depends on specific regional factors. We expect that by 2020 there will be at least one major competitive renewable energy source in most countries. The exact future mix will vary by region, depending on the availability both of renewable resources and grid infrastructure and on their contribution to the local economy. Germany for example, whose government has defined a vision for the country’s energy future that strongly emphasizes renewable sources and energy efficiency, is currently pioneering a total transformation of its energy sector.

Iván Martén is a senior partner at Boston Consulting Group. He has been the global leader of BCG’s energy practice since 2008 and previously was the European leader of the practice.
Jerry Taylor: The Best Prediction: Who Knows?

The prospect of economically competitive renewable energy is like the horizon; it continues to recede even as we march double-time toward it.

Proponents argue—correctly—that production costs in the electricity sector have declined markedly over time. But, alas, so have the costs of gas-fired electricity, renewables’ main competitor for new plant orders. The revolution in hydraulic fracturing suggests that renewables are unlikely to win the race against gas in the foreseeable future. Wind energy would seem to be the most commercially viable renewable energy source at present, but even so, it’s not competitive with gas. Solar energy is even less competitive either on a utility-scale or at the point of use.

In the transportation sector, we see something similar; corn ethanol—the main renewable in play—has become less expensive to produce over time but, alas, it is still substantially more expensive than conventional gasoline in wholesale markets. Last week, for instance, gasoline was selling for an average of $2.76 per gallon in U.S. wholesale markets. To get the same energy content that a gallon of gasoline will get you, one would have to pay $4.06 for ethanol in those same markets.

But past is not necessarily prologue. Technological innovations are possible and scientists and engineers tell plausible stories about how any number of R&D projects currently under way could radically change the economics of renewable power. Of course, we’ve heard these stories for years, but past failures to achieve breakthroughs don’t necessarily guarantee future failures.

Which renewable has the best chance of breaking through? No one really knows because no one can reliably predict which of the many ambitious R&D projects—if any—has the best chance of success. And no one can confidently predict what will happen to conventional energy prices…the other important factor in this equation. Confident predictions have been offered in the past but, as Vaclav Smil demonstrates in his excellent book “Energy at the Crossroads” (MIT Press, 2005), those predictions have been, without exception, not worth the paper they’ve been printed on.

All we can say for certain is that the government has no better crystal ball than the private sector so the former should not be second-guessing investments made by the latter.

Jerry Taylor is a senior fellow at the Cato Institute in Washington, D.C. He has written studies on energy taxes, the oil market, electricity regulation, energy efficiency, renewable energy, sustainable development and trade and the environment.
Michael Levi: Three Reasons Solar Will Succeed

If I had to bet on one renewable source ultimately making a very large impact it would be solar. There are three big reasons to look to solar over other renewable energy supplies.

Solar can take advantage of improvements in materials, computing and nanotechnology in ways other technologies can’t do nearly as effectively. Energy innovation is at its most powerful when it can leverage gains in other sectors. Solar also has a host of initial niches it can grow in, from rooftop generation in places like California, to off-grid and micro-grid energy in often-sunny developing countries that lack good infrastructure. Having moderate-sized markets to grow in is critical to scaling technology and bringing costs down. Solar is also a much better match for our energy demand than wind is. Solar power peaks when it’s hot—exactly when people want to crank up their air conditioners. Wind power peaks in the middle of the night when people are using a lot less power.

The biggest barrier for solar is probably the cost of installing it—even if solar panels were free, the technology still would often be uneconomical. That will need to change for solar to fully take off. As I argue in a new book out in a couple of weeks, it would be unwise to bet on any renewable energy technology as our energy savior, but it would also be unwise to write renewables off.

Michael Levi (@levi_m) is the David M. Rubenstein senior fellow for energy and the environment and director of the program on energy security and climate change at the Council on Foreign Relations. His book, “The Power Surge: Energy, Opportunity, and the Battle for America’s Future,” will be published in April.
Mark Thurber : Look Out for Wild Cards

Wind and solar technology are already on a scale where they can be considered “major” in some jurisdictions (e.g. wind turbines in Denmark, solar PVs in Germany). However, almost all large installations of these technologies have occurred only because of strong (and costly) government incentives. Unsubsidized wind is borderline cost-competitive where wind resources are good, but solar remains far out of the money just about everywhere. (One mistake people sometimes make in declaring solar to be at “grid parity” is to compare the levelized cost of solar generation with the retail price of electricity, rather than to the levelized costs of other energy technologies.) Parts of developing countries that lack grid access and cheap fuel supplies may be an exception where small solar can already find a viable economic niche even without big subsidies.

Energy from intermittent renewable resources like wind and solar will continue to be disadvantaged by the fact that they can’t be turned on whenever they are needed, at least until:

1) Electricity storage technologies become much cheaper, and/or

2) Regulators permit dynamic pricing of electricity that sends price signals to consumers to conserve when intermittent resources are unavailable.

Making progress in these two areas could help wind and solar become more important contributors to our energy supply, as could finding ways to expand transmission infrastructure from where renewable energy resources are best (e.g., for wind, in the middle of the U.S.) to where most people live.

The most intriguing renewable energy technologies are those that have the most room to improve. Continued incremental improvement in wind and solar PV technologies should keep adding up over time, but the fact remains that these technologies have been around for a long time and are comparatively mature. More surprises may come from wild cards with which there is less experience. Perhaps concentrating solar power can make significant strides as we learn from the first large installations. Maybe the same subsurface expertise that has made unconventional oil and gas economic can lead to breakthroughs in enhanced geothermal systems, in which a hydraulic-fracturing-like process is used to create channels in rock through which fluid is pumped to absorb the heat at greater depths.

Mark Thurber is associate director at the program on energy and sustainable development at Stanford University. His research focuses on the role of state-owned enterprises in fossil-fuel production as well as how to deliver energy to low-income populations.
Kate Gordon : It Depends Where You Are

This is one situation where the right answer really is “All of the above.” Energy issues are inherently regional: Different parts of the country have different natural resources and energy needs. We see that in the oil-and-gas sector, with big new discoveries in North Dakota and California, but no major resources in the upper Midwest and Pacific Northwest, for example. Same goes for renewables: Some parts of the U.S. are windier than others, some are sunnier, some have better access to hydroelectricity or geothermal resources…. You get the point.

But unlike traditional energy sources like oil, gas and coal, renewable energy can be “extracted” in every single state in the nation. In a paper I co-wrote last year for Next Generation and the Center for American Progress, we identified six distinct advanced energy regions in the U.S., each with its own unique strength in a particular form of clean energy. These regions have found competitive advantage in their ability to build on these strengths to innovate, manufacture, and deploy clean energy for their own residents, and for export to other regions.

As for the time frame: Renewable energy is already a major energy source. Even here in the U.S., where we have yet to make a national policy commitment to renewable energy (and where fossil fuels are still heavily subsidized), we’re still deploying enough to make these technologies cost-competitive. Wind energy, for example, is already the cheapest new source of electricity in many parts of the country, and in fact more megawatts of wind energy were installed in 2012 than any other kind of generation, including natural gas. Solar, too, is booming: Citigroup C -0.27% recently reported that rooftop solar has already reached residential “grid parity” in California. And just imagine how cheap these renewable technologies would become if we decided to charge the real social cost of burning fossil fuels, which would add between 14 and 35 cents per kilowatt-hour.

We’re beyond talking about the promise of renewable energy. It’s a reality. It’s time now to talk about how to make it a far bigger part of our nation’s energy future.

Kate Gordon (@katenrg) is vice president and director of the energy and climate program at Next Generation. She previously served as vice president for energy and environment at the Center for American Progress.
Jeffrey Ball : Solar’s Future Seems Bright

Most predictions about the future of energy turn out to be wrong. Oh, well. Here’s one: Solar power could prove a big, though probably not dominant, energy source over the next couple of decades.

Solar today is a negligible part of the global energy mix. It provides a fraction of 1% of world-wide electricity, the International Energy Agency says. Moreover, solar companies now are suffering, and many more are likely soon to fail. The industry is being walloped by declining government subsidies for its subsidy-dependent products and by massive overcapacity, which is turning its profits into losses.

But those are short-term problems. Longer term, solar’s future seems bright. The cost of producing polysilicon-based solar panels—today’s dominant solar technology—has plummeted over the past two years. In a few spots around the globe—places with lots of sun and quite high electricity prices—solar today is starting to compete on price with conventional power (albeit when taking into account the tax breaks these energy sources get).

One sign of solar’s emergence is that it’s scaring many of today’s dominant producers of conventional power. E.ON, EOAN.XE -1.15% the big German utility, reported a loss in last year’s third-quarter that it blamed partly on solar. Enough E.ON customers were putting solar panels on their house roofs, minimizing their demand for peak-time electricity from E.ON’s fossil-fueled plants, that E.ON’s profits were materially eroding. And last month, David Crane, chief executive of NRG Energy, a big U.S. power producer, called distributed solar power a “mortal threat” to companies such as his.

Fossil fuels aren’t going away soon. But huge innovation is under way to come up with new solar technologies that could prove game-changers. It’s crucial not to get blinded by the light. But it’s also worth recognizing what may be over the horizon.

Jeffrey Ball (@jeff_ball), formerly The Wall Street Journal’s environment editor and a longtime energy reporter at the paper, is scholar-in-residence at Stanford University’s Steyer-Taylor Center for Energy Policy and Finance, a joint initiative of Stanford’s law and business schools. He writes about energy and heads a project exploring the relationship among countries in the globalizing clean-energy industry.
Ariel Cohen : Energy Is Not a Matter of Religious Faith

Renewable energy is not going to come from one source, but from a number of technologies, including solar and wind, which for now appear to be the leaders in renewable electricity generation.

Different U.S. states and different regions of the world will have different energy mixes, including among the renewables. However, it is important to remember that for now these technologies are not competitive, BTU to BTU, with fossil fuels, if the government phases out the current tax credits. Energy is not a matter of religious faith, and technologies should not receive open-ended subsidies just because someone “wants to believe.”

A separate issue is renewable transportation fuels. These may come from algae or a number of agricultural sources, but again, so far, these are not competitive. The fiasco of corn ethanol is widely known. The closest one gets to competition is sugar-cane ethanol, but only when oil-based gasoline is relatively expensive.

The 2012 U.S. Department of Energy renewable fuels study postulates that 80% of electricity generation in the U.S. by 2050 will be from renewable sources based on known technologies and excluding possible breakthroughs and novel technologies such as enhanced geothermal; ocean energy, including wave, tidal, current or ocean thermal; and floating offshore wind technology.

Dispatchability, the ability of suppliers to exercise control over an alternative energy plant’s increase and decrease of supply, will remain one of the key challenges in wind and photovoltaic solar.

However, with the abundance of shale gas obtained through fracking and horizontal drilling and development of the global LNG markets, these renewable technologies are likely to face serious barriers to entry, or remain noncompetitive, unless governments introduce carbon taxes or cap and trade which would distort markets drastically. Such a high economic price for renewables appears unwise, especially as the debate over the human causes of climate change continues, and as major emerging markets polluters, including China and India, are unenthusiastic about joining an equitable and global carbon tax or capture regime.

Ariel Cohen (@Dr_Ariel_Cohen) serves as a senior research fellow in Russian and Eurasian studies and international energy policy at the Heritage Foundation. He has published six books and monographs, 30 book chapters and over 500 articles.
Mazen Skaf : Hydropower’s Dominance Will Continue

A renewable energy source that is already a major source of energy today is hydropower (global installed capacity of hydro exceeds 980 GW). Excluding hydropower, several renewable energy sources are on track to deliver an increasing share of total energy supply over the next 10 to 20 years. Specifically, wind, concentrated solar, biomass, geothermal and solar PV carry the most promise (with variations across markets depending on resource availability, policy programs, and competing energy sources).

By 2040, wind-powered generation is projected to account for about 7% of global power supply. Wind power is already among the most competitive renewable technologies. The levelized cost of electricity (LCOE) for new onshore wind farms ranges between $0.05 to $0.15/kWh (based on a cost of capital of 10%). In locations with good wind resources, onshore wind is becoming competitive with fossil fuel-based generation.

Solar-powered generation is projected to account for about 2% of global power supply by 2040. The costs of concentrated solar and solar PV are declining due to steep learning curves and large deployments in recent years. In the case of solar PV, for instance, it is estimated that every doubling of installed capacity will yield a reduction in module costs of about 22%.

Even as a relatively mature technology, hydro will continue to attract attention due to the advantages it offers: Lowest LCOE, grid stability, and potential for energy storage and complementarity with other renewables. Further, hydropower (including small hydro) provides options for building additional capacity at existing facilities or installing generation capacity at dam locations with no current generation at attractive marginal investment costs in the range of $500 to $800/kW.

The long-term projections for expansion in the use of renewable energy are sensitive to natural gas prices, innovation in storage technologies (including batteries), policy programs and the relative costs of alternative generation sources. It is important to take a portfolio approach to renewable energy sources and their share of total energy supply whether at the level of a specific geographic market or globally.

Mazen Skaf (@Skaf777) is managing director of the Europe and Middle East practice of the U.S.-based management consulting firm Strategic Decisions Group. He advises clients in energy and related industries on strategy, financial-risk management, negotiation analysis and deal structuring.
Todd Myers: Whatever the Market Decides

Let’s imagine we are in the year 2025 and tidal power accounts for 10% of electric generation. That would be a dramatic increase. By that time, however, giving homeowners more control over their energy using the Smart Grid could reduce demand by a similar amount. If a penny saved is a penny earned, why would we focus more on “renewable” tidal power than technologies yielding the same carbon emissions reduction and energy savings?

Given a choice between algae-based biofuel or expanding high-speed Internet access to encourage telecommuting and reduced fuel use, which should we choose? Does it matter that one is a “renewable” energy source and the other isn’t? This is the beauty of the free market. As long as there are costs to energy use and the impacts of energy use, the free market treats all approaches equally, without politics, as long as they effectively save resources. Given a choice between solving our energy and environmental demands by narrowing our focus to a few choices or expanding our vision to include any approach that conserves energy, we will be more successful by embracing all potential options.

This is the danger of politically chosen technologies. The perspective of policy makers is limited and it can never match the combined creativity of the many investors and inventors looking for the next opportunity to profit from their risk-taking in the marketplace. For decades, we’ve been promised that solar energy would be price competitive. Just a few years ago, Congress expected cellulosic ethanol to blossom as an energy source. Neither occurred. Numerous other technologies have been touted and then have floundered. That is the nature of innovation. We are wiser to reduce the costs of taking risks in the process of discovering new technologies than to guess what technologies will emerge.

Todd Myers (@WAPolicyGreen) is environmental director at the Washington Policy Center in Seattle and author of “Eco-Fads: How the Rise of Trendy Environmentalism is Harming the Environment.” He also serves on the Washington state Salmon Recovery Council.

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