“If you look at the average wind or solar site alone, there’s a good amount of time each day that it’s not generating electricity,” explains Palmintier. “But if you combine all the wind and solar sites together, you find that 90 percent of the time you can get seven megawatts out” of facilities that at peak production might generate 100 megawatts.ONE OF THE BIGGEST DRAWBACKS INVESTORS and utilities have found with solar and wind power is that they are “variable.” Simply put: they can’t generate electricity when the sun’s not shining or the wind isn’t blowing. That’s problematic because we’ve grown accustomed to getting energy whenever we want it. Flick a switch and the lights should go on, regardless of whether it’s sunny or windy outside.

In the past, utilities believed that they had to compensate for this variability by installing more traditional, fossil-fueled power plants. The more wind or solar power on the grid, the thinking went, the greater the need for backup generating facilities to be there when the wind or sun wasn’t.Enter RMI’s Energy & Resources Team. Over the past year, Senior Consultant Lena Hansen has led a series of research projects to rethink the implications of wind and solar’s variability. In the process, she and her colleagues are re-evaluating the economics of putting more renewable energy on the grid.

The key, according to Hansen, is for utility managers to think of all their wind and solar installations as a portfolio.

“No person would invest in just one stock,” says Hansen. In the financial markets, most people forego the huge risks and potentially large gains of owning shares of one company for the reduced risk and smaller rates of return of owning shares in multiple companies, she explains.

Hansen argues that the same should go for utilities investing in wind and solar. “By diversifying the portfolio of sites, you mitigate variability,” she says. “Put another way, the wind blows differently in different locations. So spread out your resource to reduce total variability.”

The trick is to balance risks and rewards. Very windy and very sunny sites produce more power than sites that are less windy or less sunny. But they also tend to be more variable.

Ultimately, explains Hansen, utility managers have to make a tradeoff between variability and power output. However, by modeling a bunch of geographically spread-out sites, Hansen and her colleagues hypothesized, utilities can start to make educated guesses about the optimal portfolio—one that maximizes power generation and minimizes variability. To test the hypothesis, Hansen and former RMI fellow Jonah Levine compiled hundreds of tables of meteorological data for a one-year period, then set about looking for overlaps in the times when the wind is blowing.

By combining multiple wind sites with solar generation, total power generated for the grid becomes much more stable. This potentially replaces base load generation sources such as coal and nuclear. See full article here: http://ert.rmi.org/news/ert-news/getting-a--firm--grip-on-renewables.html

 ***Thailand can do this too. However, Thailand Gov. needs to install the the "Unflied Power Grid" to share Renewal generated electricity everywhere in Thailand. There's good Wind power potential in the Southern provinces and very good Geo-Thermal potential in the Northern provinces. And plenty of solar in all provinces.Now is the time to do it. Commodity prices are down and KhunThai's need jobs.Quit buying natural gas from the murdering dictators in Burma!!!        

The other choice you have of course is HOT ROCK energy

Simply put it means you find hot spots up to 6klm below the earth's surface where the is a mass of bed rock with water above it. You the drill 2 holes into the super heated water. Build a steam generator and pump up the super heated water to drive the generator thus producing GREEN power, then pump the cooled water back down to get re heated It is a closed cycle. They are trailing this process is Sth Australia righ now and have 2 very small generators producing 5 giga watts each. Once the trail is over they will go into full production. It is a very exciting time for this technology. Research ahs estimated Australia has enough HOT rock area's to satisfy all Aust power need for the next 400 yrs !!!

http://www.petratherm.com.au/hotrock/index.htm

http://www.pir.sa.gov.au/__data/assets/pdf_file/0011/87437/PAPER_Hot_Rock_Energy_Projects_-_Australian_Context_Goldstein_et_al,_20-23_Oct_08._SPE-117457-PP.pdf

One of our biggest customers is a Petroleum producer who has in recent years "greened" it's portfolio. In 2008 the investments in 'Green Energy' exceed USD 5Billion with an estimated 'stand alone' recovery of costs at around 300years but ROI estimated at 10-15 years (as part of their marketing plan). Unfortunately too many of these initiatives are symbolic gestures...a bit like the McDonald's Salad...