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Fossil fuels still dominate primary energy consumption in United States but the popularity of renewable energy sources continues to grow. According to a latest report from Worldwatch Institute U.S. invested more than $50 billion in renewable energy sources in 2011.

There are various reasons behind this huge investment. Renewable energy sources do not only ensure diversified energy portfolio that can reduce nations heavy dependence on foreign fuel import but they also provide us with an environmentally acceptable energy option, one that can be quite helpful against climate change. 

Fossil fuels, when burn, release harmful greenhouse gas emissions, which leads to global warming and rapidly growing climate change impact. Using more renewable energy sources instead of solely relying on fossil fuels therefore means improving environmental condition of our planet, and reducing the negative effects of climate change. 

Sadly, if we look at global energy consumption we can see that renewable energy sources are way behind fossil fuels, with many energy experts estimating that fossil fuels will likely remain dominant energy sources for the foreseeable future.

At the end of 2010 renewable energy sources accounted for 11.1 percent of energy produced in United States. The list of most important renewable energy sources in United States includes: hydropower, wind power, solar power, geothermal power and biomass.

Hydropower is renewable energy source that has long tradition in United States. It is currently the most important renewable energy source in the country, with around 7 percent of nations total power being produced by hydroelectric power plants. Hydroelectric plants arent necessarily connected with a large dam as in recent times we can see some hydroelectric power plants that just use a small canal to channel the river water through a turbine. Hydropower is not 100% environmentally friendly source of energy but when compared with environmental damage done by fossil fuels, its environmental impact is minimal, especially in correlation with current regulations and new environmental policies Hydropower, beside being reliable and one of the most cost-competitive renewable energy sources, can also provide some other important services beside generating electricity like irrigation, recreation, water supply, etc.

Wind power was for many years the fastest growing renewable energy source in the country, and has only recently being left behind solar power in terms of growth. U.S. was also for many years, global wind energy leader in terms of capacity, but in the last two years it trails China, as it cannot follow Chinas rapid pace. The U.S. states which lead the way in wind energy development are Texas, Iowa and California. Texas is also the home to the worlds largest wind farm, namely the Roscoe Wind Farm with the capacity of 780 MW. At the end of the 2011 wind power in the U.S. provided enough electricity to satisfy the need of almost ten million U.S. homes. The insecurity about the renewal of wind energy tax credit is hurting U.S. wind energy industry but regardless of this wind energy should still remain one of the top renewable energy sources in the country.

Solar power industry is the fastest growing industry in the country with many states offering significant incentives for solar energy systems. The prices of solar panels have fell by more than 40% in the last few years and solar power is more popular than ever before. However, even despite this strong growth, solar power still satisfies less than 1% of total U.S. energy needs. The sunny state of California is the leading U.S. state in installed solar power capacity with the capacity of over 500 megawatts. U.S. is still not the largest photovoltaic market in the world as it trails the leader Germany.

U.S. is the world leader in both installed capacity of geothermal energy as well as in the generation of electricity from geothermal energy. Geothermal power has half of century old history in United States with the first geothermal power plant opened at The Geysers in California, back in 1960. Geothermal power plants are concentrated in the West, and most geothermal power is generated using steam or hot water from underground. Geothermal energy currently meets less than 1% of U.S. power needs though some studies have showed that just western states have the potential to provide over 20 percent of national electricity needs. California leads the way in geothermal capacity, followed by Nevada.

The use of biomass is growing in United States, and currently provides about 4% of the total energy used in the country. Biomass does not only play the important role as a renewable energy source that generates electricity but can be also considered as a vital part of U.S. waste management infrastructure. The largest biomass energy resource in U.S. is still wood, followed by waste. Biomass power has great potential because it has origin in plant sources meaning that it can potentially be produced almost anywhere in the United States (plants can be re-grown time and time again on the same piece of land).

Renewable energy is still to achieve full renaissance in United States. The clean energy industry is still in need of government and state incentives in order to remain competitive with fossil fuels. The clean energy future still looks many years away but its definitely a reachable goal. However, U.S. will have to significantly improve its renewable energy policy with federal renewable energy standard as the preferred thing to start with.

ReNew Economy has a pair of articles looking at the benefits provided by solar power during the recent heatwave in southern Australia - Solar saved southern states from new and costly demand peaks.

Victoria and South Australia have just finished a week which put the highest stress on the electricity grid since a similar heatwave occurred on 28th-30th January 2009. Despite the population of Victoria and South Australia increasing at least 7%2 since then, the electricity demand supplied by the grid during the heat wave was just lower than the peak usage reached on the 29th of Jan 2009.

Electricity demand from the grid in the recent heatwave peaked on Wednesday. There were initially warnings of potential load shedding1 from the grid operator after the usually baseload Loy Yang A3 brown coal unit and one of the Torrens Island gas units tripped offline on Tuesday. However, demand came in slightly lower than forecast and apart from some minor local transmission outages, demand was fully supplied. ...

If no solar had been installed, Victoria would have set a new demand record of 10,675MW at 1:55pm today 17th-Jan-2014, higher than the metered demand of 10,572MW used at 12:35pm on the 29th-Jan-2009. South Australia would have set a new demand record of 3,549MW at 4:30pm yesterday 16th-Jan-2014, higher than the metered demand of 3,441MW set 4:25pm on the 29th-Jan-2009. Solar reduced the maximum combined VIC & SA demand by 448MW.

Asking what happens when the sun doesn’t shine and the wind doesn’t blow ignores the spare capacity built into the grid to handle record demand days like yesterday and today. For the majority of the year, spare generation capacity can backup variations in solar or sudden failures at fossil fuel plants. Record demands, where there is little spare capacity, are caused by hot conditions and strong sunlight. Solar is now a critical component of the generation fleet that reliably supplies our power.

An the second from Giles Parkinson - Solar puts heat on big generators as demand peaks subside.

There seems no doubt that solar is playing a key role in moderating demand and stress on the grid.

It’s interesting to note that the differences between the peaks of previous years – such as in 2009 when there was little solar – correspond with the amount of solar that has been installed (notwithstanding the need to add in population and air-con growth, offset by more energy efficient appliances and less manufacturing).

On Wednesday, for instance, the interval peaks were 10,110 MW in Victoria and 3,108MW in SA. The corresponding numbers on January 29, 2009, were 10,446 MW and 3,270 MW. According to the APVI’s Live Solar website, the PV contribution at the peak times was around 220 MW in each state. Some suggest that without solar, Victoria would have hit record demand from the grid on Thursday – and prices to boot.

In WA, the peak in electricity demand has fallen well short of previous years, despite the record-breaking streak of temperatures, rising population and growing use of air conditioning.

In 2011 and 2012, peak demand peaked at more than 4,000GW. In the past week, it made it only as high as 3,733. How much solar does WA have on its rooftops? About 340MW.

This has had an impact on peak pricing events. In 2009, the average spot price between 8am and 4pm was over $6,000/MWh. The average price – despite a few peaks – in the latest period has been about one tenth of that.

On Thursday, the volume weighted pool prices between 08.00 and 16.00 yesterday were $299/MWh in Victoria and $377/MWh in South Australia, despite the huge levels of demand. The reaching of super peaks of $12,000/MWh or more in Victoria occurred mostly when Loy Yang A – the biggest brown coal generator – had one of its four units off-line for urgent repairs .

Generators and retailers use elaborate hedging policies to reduce their exposure to such fluctuations – which can be triggered as much by bidding tactics and other factors as much as weather – but the fact remains that a large revenue pool has been evaporated by the impact of solar.

In the same way that one third of the network costs are to cater for about 100 hours of peak demand a year, generators source a huge amount of their annual revenue from similar events. The problem for many coal generators is that they grew to rely on these peak pricing events to boost their revenue, and inflate their values. Solar eats into those revenues whenever they produce – because the output comes during the day-time period, when prices are normally higher.