A group of researchers has released a study that claims to shoot down the common perception that clean, renewable energy from wind and solar sources is all well and good, eco-wise, but that it's too uncertain, sporadic, and pricey for widespread use.

"These results break the conventional wisdom that renewable energy is too unreliable and expensive," said professor Willett Kempton of the University of Delaware in a statement. "The key is to get the right combination of electricity sources and storage – which we did by an exhaustive search – and to calculate costs correctly.”

This good news is detailed in a paper available online now and scheduled to be published in the March 2013 issue of the scholarly Journal of Power Sources, straightforwardly entitled "Cost-minimized combinations of wind power, solar power and electrochemical storage, powering the grid up to 99.9% of the time".

When Kempton referred to an exhaustive effort, he wasn't merely whistling the proverbial Dixie. The six authors of the paper used computer modeling to study 28 billion – that's with a "B" – combinations of energy sources and storage techniques. Each of those 28 beeeelion combos were tested against four years of actual hourly weather data, along with electricity-demand data from PJM Interconnection, a power grid that serve 13 states from New Jersey to South Carolina to Illinois – about one-fifth of the US grid.

Big enough sample for ya?

As a result of this intensive modeling effort, the researchers say they've discovered that a carefully designed combination of renewable sources – wind and solar – with batteries and fuel-cell electricity-storage systems could by 2030 supply enough power to keep a large electrical grid fired up 99.9 per cent of the time, and do so at a cost comparable to today's not-so-renewable energy grid.

Four years of historical data applied to a mega-sized renewables, storage, and fossil-fuel grid model

Cost was central to the team's work. With this in mind, one of the things that they discovered is that it's cheaper to crank out more juice than needed during hours of average need – as much as three times as much – than it is to store all the extra energy for later use. Those batteries and fuel cells ain't cheap.

One of the key elements in their plan would be to have a widespread geographical distribution of such intermittent sources as wind farms and photovoltaic installations – when it's windy and sunny in one location on the grid, it could be calm and overcast in another and all parts of the grid would have enough power.

Another aspect of their plan is to use some of that extra renewable capacity, when it's available and when storage capacity is full, to substitute for natural gas for home and business heating.

Fossil-fuel sources wouldn't be abandoned entirely. There would likely be times when neither wind nor solar could provide enough juice, and when storage had been depleted. When that happens, they say, it'd be time to fire up the ol' CO 2 spewers and spin their turbines. Doing that, however, would be a last resort, and not the first, as is true in much of the US's power grid today.

While the idea of a large, geographically diverse renewable-energy grid might seem heinously expensive, the paper's authors contend that if current estimates are correct that by 2030 wind and solar capital costs will be about half of what they are today, by that date a renewable system would be as cost effective as a fossil fuel system, and all without government subsidies.

There is one cost sweetener in their calculations, however: their cost estimates for that comparison includes the costs related to the human health effects of fossil fuel–caused air polution.

Those are costs, of course, that are not borne by the electric power industry. Yet. ®