* The authors of the study developed a computer model to consider 28 billion combinations of renewable energy sources and storage mechanisms, the University of Delaware reported on Monday.
* These combinations were tested over four years of historical hourly weather data and electricity demands collected from the regional PJM Interconnection grid, which represents one-fifth of the United States' total electric grid.
* What the researchers found is that generating more electricity than needed during average hours would be cheaper than storing excess power for later high demand.
* When more renewable energy was generated than needed, the model first filled storage, then used the remaining to replace natural gas for heating homes and businesses. As a last resort, the excess energy generated would go to waste.
* Because of variances in weather and season, reliability is a big factor in an electric system largely dependent on renewable sources, the university reported. According to the research, reliability could be achieved by expanding the geographic area of renewable generation, using diverse systems, employing storage systems, and burning fossil fuels as a backup.
* Storage is a costly issue with large-scale renewable energy use, as the storage medium -- batteries or hydrogen tanks -- must be larger for each additional hour stored.
* According to the university, the study estimated technology costs in 2030 without government studies. These costs were compared to the costs of fossil fuel generation today, determining both the fuel cost itself and the external costs such as health effects caused by power plant air pollution.
* The university reported that research shows projected capital costs for wind and solar in 2030 at about half of today's wind and solar costs, while maintenance costs are expected to remain the same.
* Establishing newer and more affordable forms of energy storage has captured the interest of the Obama administration, which$120 million for a Joint Center for Energy Storage Research at the Argonne National Laboratory in Illinois.
* Upon announcing the award to the Argonne project -- which involves a collaboration of universities, national laboratories and private firms -- Energy Secretary Steven Chu stated, "Based on the tremendous advances that have been made in the past few years, there are very good reasons to believe that advanced battery technologies can and will play an increasingly valuable role in strengthening America's energy and economic security by reducing our oil dependence, upgrading our aging power grid, and allowing us to take greater advantage of intermittent energy sources like wind and solar."