Storage Boosts the Power of Renewable Energy

During the conference experts showed how energy storage can play a variety of roles in firming up renewables at different time scales, i.e. from moment to moment, daily, weekly and seasonally. The presentations showed how storage options are essential for expanding renewable energy sources, stabilizing the grid, ensuring a continuity of supply, increasing energy autonomy and mediating against intermittent power production.

As storage technology advances, decision makers are starting to create a more favorable policy environment for innovators. For example, the U.S. Energy Storage Technology Advancement Act of 2007 recognizes the crucial roles that storage can play.

"This bill is the first official recognition of the importance of energy storage by Congress," said Imre Gyuk, Manager of Energy Storage Systems Research with the Department of Energy. "It is only an authorization bill and thus carries no appropriated funding, but it is a wonderful platform for future requests for storage research, demonstrations and development."

The act establishes an Advisory Committee (the Energy Storage Advisory Council), and authorizes funds for a basic and an applied research program of US $50 million and $80 million, respectively, for each fiscal year from 2009 to 2014. It also provides US $100 million each year for up to four energy storage research centers; US $30 million a year for energy storage demonstration projects and vehicle energy storage demonstration; and US $5 million a year for 10 years for secondary applications of electric drive vehicles.

Reaction to the act has been positive and the storage industry is beginning to take off.

"Grid-scale storage is here now," said Ed Cazalet of MegaWatt Storage Farms. "Storage should be deployed now at the gigawatt (GW) scale...where capacity, ancillary services and energy time-shifting are clearly needed."

Storage projects can be sourced close to loads, on the grid or at the generating facility. In his presentation, Cazalet emphasized that the demand-pull from large-scale commercial deployment will encourage manufacturing investment, lower costs through volume production (economies of scale) and lead to the commercialization of advanced technologies.

The benefits of storage are significant, especially in integrating distributed generation. Storage protects against mistakes in forecasting, removes barriers in connecting renewable sources to a variety of grids, shifts demand peaks by storing off-peak energy to sell back to the grid during peak times, provides frequency regulation and deters expensive grid upgrades.

With current costs on average of US $1000 to 1500 per kW installed (see CaISO's "Integration of Renewable Resources" report), storage application companies realize the importance of gaining multiple revenue streams so that the technologies will come down in cost through volume production and experience. However, for some storage technologies like pumped hydro storage, costs range from US 0.1 to 2 cents per kWh (see ESA's Technology Comparisons, Capital Cost). Analysts say that governments need to create practical incentives so that storage options can be rapidly expanded to support large deployments of wind and solar power at great scale.

Jim Kelly of Southern California Edison defined storage as the "game changer" of the industry, allowing utilities to "inventory" electricity for the first time. SCE has proposed installing 250 MW of utility-owned rooftop solar PV on large commercial rooftops, claiming that this will transform the U.S. PV market, while utilizing unused rooftops. Kelly asserted that if storage was coupled with PV it could shift the peak from noon to later in the afternoon, remove intermittent output and provide emergency back-up power.

In addition, since substantial wind resource capacity is often present at the fringes of existing grids and because fluctuating wind speeds can produce substantial variations in wind energy generation over wide areas, analysts also note that forecasting needs to be combined with rapid-cycle energy storage to smooth intermittency and better integrate renewable resources into the grid.

VRB Power Systems, a Canadian storage company is doing just that. VRB vanadium flow battery technology is already smoothing wind turbine output for remote power hybrid wind-diesel applications in northern Canada and Alaska and providing frequency regulation, voltage support and blackstart capability.

These locations have turned to wind power because electricity costs have become unreasonably high due to the growing costs of diesel generation and to gain the environmental benefits associated with a renewable resource. A VRB flow battery is introduced to the hybrid wind-diesel system to firm up the wind power and to ensure that the generator runs on the most efficient setting. "With the current high cost of diesel in these remote communities, the pay-back for investments in storage is very attractive," said Brian Beck of VRB Power Systems. VRB claims that solar can also be added to this system.

With over 200 megawatts (MW) of NaS batteries installed worldwide, Japan-based NGK Insulators, Ltd is another battery storage company hoping to capitalize on that rapidly growing market. The company's NaS batteries, used mainly for load leveling, enable companies to sell cheap off-peak wind power during peak times, thereby fetching a higher price. There are 34 MW of these batteries being installed near the 51-MW Rokkasho wind farm, making it the largest combined wind and storage project in Japan. Stored indoors to protect them from the corrosive salty air of the region, 17 sets of 2-MW NaS battery units (each battery unit consists of 40 50-kW modules) are monitored alongside the weather and the Rokkasho wind farm in a control center.

New technological applications such as the sophisticated vanadium flow batteries of VRB Power and the NaS systems of NGK combined with a variety of other storage options such as pumped hydro and compressed air systems demonstrate that the intermittency concerns often associated with renewables like wind and solar are quickly becoming manageable issues.

Lynda O'Malley is currently completing a Masters degree focusing on Renewable Energy Solutions at York University. She is also contributing researcher for the Pembina Institute, a Canadian policy research and advocacy organization specializing in sustainable energy solutions. Ms. O'Malley is also organizing the Storage and Smart Grids workshop for the 7^th World Wind Energy Conference taking place in Kingston, Ontario June 24^th-26^th, 2008.