How can energy storage integrate renewables into our power grid?

Posted on Apr 18, 2016 in Blog | 0 comments

One emerging advancement in the clean energy sector is energy storage – particularly as it applies to storing renewable energy on the electric grid. The energy from renewable fuel sources can be stored at any point in the electric distribution system – at power stations, along transmission, lines, and near customers. Energy storage holds many potential benefits:
– It could optimize the availability of renewable energy, which is naturally intermittent;
– Stored energy could alleviate energy shortages and blackouts as back-up fuel supply;
– Power from energy storage systems can be dispatched more quickly than from gas-powered combustion turbines, making power supply from the grid more flexible. This will allow utilities to quickly respond to fluctuating demand between peak and off-peak capacity;
– Reduction of the operational costs of power generation – both due to the use of renewable energy (no fuel costs) and its contribution to meeting peak demand, which is capital-intensive to generate;
– Lower environmental and energy costs due to reduced carbon emissions and reduced water consumption.

The success of energy storage projects also depends on its overall cost-competitiveness to alternative power production systems.

Energy storage technologies include:
Batteries: these can include solid-state batteries and flow batteries. Solid state batteries have a range of electrochemical storage solutions, and flow batteries store energy directly in the electrolyte; examples include liquid metal batteries, redox flow batteries;

Flywheels: a mechanical way to generate electricity using rotational energy;

Thermal storage: using stored heat to produce electricity;

Pumped hydro-power: using compressed air to store energy;

Compressed Air Energy Storage: utilizing water reservoirs as energy storage.


Current energy storage projects in the U.S.

Eagle Mountain Project – pumped hydro
Desert Center, CA

This pumped hydro project is built on the former Eagle Mountain Mine – operated by Kaiser Steel Co. – which got converted to a hydroelectric project under authorization of the FERC, receiving its license in 2014. The mine pits were converted to reservoirs, and water flow down to lower pits generates electricity. The project will utilize four 325 MW reversible hydroelectric turbines and have a 1300 MW generating capacity. The pumped hydro project will store energy produced by windmills, solar panels, and baseload nuclear and fossil fuel plants. Total costs are $1.4 billion.

Potential environmental and economic benefits

This energy storage project is anticipated to help California reach its mandated Renewable Portfolio Standard of 33% renewable share of energy by 2020, contributing to an overall reduction in carbon emissions. Because the project was converting an already existing site, capital and operational costs are low. It is linked to a river, but otherwise uses a closed-loop system for water supply, and will not disrupt the aquatic environment. The project will create up to 100 construction jobs, 30 operational jobs, and provide tax revenues to county and local governments.
For more information:

Advanced Underground Compressed Air Energy Storage (CAES) Project with Saline Porous Rock Formation – compressed air storage,
Kern County, CA

The CAES project at a Pacific Gas & Electric Company demonstration plant has 300 MW generating capacity with 10 hours of storage capacity. It uses an underground storage container as the depleted gas reservoir and turbine generators using a closed-loop water system. It is co-funded by the U.S. DOE grant under The Recovery Act, California Public Utilities Commission, and California Energy Commission. The total budget for the project is $355,938,300, with the federal share being $25,000,000.

Potential environmental and economic benefits

Anticipated benefits include reduced GHG emissions and improved grid reliability, along with creation of 25 permanent operational jobs and 475 construction jobs.


For more information:

Solana Generating Station – thermal storage
Gila Bend, Arizona


A commercial project owned by Abengoa Solar Liberty Interactive Corporation – The Solana Generating Station is a 280 MW parabolic trough solar plant with molten-salt thermal storage – it generates enough power to supply 70,000 homes under a 30-year power supply contract with Arizona Public Service. The thermal energy storage system provides 6 hours of generating capacity by concentrating solar energy into a heat transfer fluid, which then heats water to produce the steam that operates a conventional steam turbine. It costs $2 billion, partially funded by the Federal Loan Guarantee Program ($1.45 billion.) The loan was issued in 2010 by DOE and the plant started operating in October 2013.

Potential environmental and economic benefits

Environmental benefits include reduced water consumption and reduction of 480,000 metric tons of CO2 emissions. Economic benefits include creation of 85 operational jobs and over 2,000 construction jobs. Operational costs of thermal storage are even lower than that of battery storage, especially when using cost-effective molten salts. Thermal storage can be used for residential end-use, where stored electricity can be dispatched in response to demand.
For more information:

Primus Power Modesto Wind Firming Energy Farm – redox flow battery
Modesto, CA

The Primus Power redox flow battery is made up of zinc and chlorine electrolyte solutions, and is being integrated in substations in Modesto Irrigation District at a capacity of 25 MW. It will be tested at PG&E with support from Sandia National Laboratories and the Electric Power Institute. Total budget is $46,700,000 with the federal share being $14,000,000.

Potential environmental and economic benefits

Anticipated benefits include reduction in GHG emissions, reduction in power costs, and increase in renewable generation. Because the electrolyte solutions are self-charging and self-regulating, manufacturing and operating costs for the battery are low. The EnergyFarm redox flow batteries are scalable, and can be scaled up to 100 MW at 250 kW units. The battery installation will allow MID to respond to off-peak demand with power supply from on-peak periods.


For more information:



Energy storage provides the promise of reducing carbon emissions, increasing share of renewables in electricity production, frequency regulation, and low operational costs. Components of energy storage systems, such as solar PV panels and molten salt used for thermal storage, are on a trajectory of declining costs. As long as component materials are earth-abundant and scalable, operational costs can remain low.

Many of the energy storage systems can be quickly dispatched. Storing energy to be dispatched at times of high demand can balance supply with demand, leveling load curves.

However, some challenges remain with how utilities deal with the high upfront costs of energy storage projects. Government grant programs and loan guarantees have provided effective top-down incentives to build energy storage systems. Utility structure (vertical utilities vs. unbundled utilities) also impact which stakeholders internalize economic benefits from energy storage. Thus, policy incentives will have to vary according to the type of utility from which customers purchase power.

Overall, the cost-competitiveness of energy storage systems is promising. Energy storage can compete with fossil fuel plants where they minimize environmental costs in addition to economic costs. They can replace existing fossil fuel plants, or provide an alternative to building a coal- or gas-powered plant.



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