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Conduit ED DR/DER Week 4: Intermittent Energy Resources and Battery Storage

Created 8/15/2018 by Conduit ED
Updated 8/16/2018 by Stephanie Lane
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The electrical grid offers a finite amount of power to the region it serves. Its capacity can grow if the infrastructure is built out, but at any given time only so much electricity is available to be distributed—which can pose a challenge when demand exceeds supply. The demand response (DR)-enabled technologies previously mentioned in this series address this challenge by reducing or shifting demand.

Many utilities are also pursuing strategies that can supplement existing grid capacity, often by storing surplus energy during off-peak hours. These energy-storage devices create opportunities for utilities to leverage intermittent resources, such as wind and solar generators, efficiently and in ways that impact the grid system more consistently. Renewable energy sources such as solar and wind are also being pursued as a supplementary energy source because of renewable portfolio standards and the decommissioning of existing coal plants.

What It Is

Because these resources aren’t constantly available and predictable, they’re referred to as intermittent energy resources. Batteries and solar photovoltaic (PV) panels are two technologies currently getting attention, with their potential DR opportunities being investigated at the large-scale and residential level.

When it comes to understanding the energy-storage potential of batteries, you have to go big. The AA battery you put in your alarm clock has nothing on the complex systems used to manage the electrical grid. These batteries can be as large as a football field, have capacity up to 100 MW (in the case of Tesla’s massive battery installation in Australia), and are powerful enough to improve grid reliability and open up new channels for storing renewable energy. They’re often lithium-ion based, the same type of battery used in electric cars, although vanadium redox-flow and recycled electric vehicle (EV) batteries are also being tested.

Many utilities are currently considering how best to leverage solar technology to impact system efficiency—particularly photovoltaic systems. Solar PV systems combine solar panels made from a semi-conducting material, an inverter, and cables to convert sunlight directly into electricity, with each PV cell producing one to two watts. The PV system isn’t complete until it’s connected to the electrical grid, drawing on the solar source to generate power that can then be distributed to utility customers.

As an alternative energy source, solar PV can generate power anywhere that soaks up the sun’s rays, whether it’s a private home on the California coast or an industrial facility in Spokane. Some experts estimate that five hours of direct sunlight can yield about 1.5 kWh per solar panel, or 500-550 kWh per panel each year, although that varies widely according to conversion efficiency, geographic location, tilt angle, and operating temperature. Connecting solar PV systems to the grid can be used by utilities to meet demand when the solar power generated is equivalent to the electrical load.

How It Works

Intermittent energy resources like these have potential to supplement existing generating resources if used strategically. Batteries can charge during off-peak periods, then be discharged at times of peak demand a few hours later, using stored energy from either the grid itself or supplemental energy sources to respond to demand increases. Some utilities are already using battery storage to manage their grid, installing batteries to address high load at a feeder level or as back-up so that power stays on during electrical outages. Batteries can contribute to load-shifting activities, with stored energy discharged into projects that need wattage. Residential batteries are also beginning to enter the market, with some early adopters willing to pay the $5,000 – $10,000 required to yield a back-up power supply of approximately 8 kW. Because this technology is relatively new, the industry is still navigating optimal sizing and integration. The resource planning models that will determine these standards have yet to be built.

Solar energy and other renewable sources can also be stored during off-peak hours using the same advanced batteries described above, then discharged later when demand increases to reduce grid strain.

Click image to enlarge

Who’s Using It

Some Pacific Northwest utilities are already exploring battery storage, including Snohomish PUD, Portland General Electric (PGE) and Pacific Power. Snohomish PUD installed lithium-ion and vanadium redox-flow batteries—both located in substations, one near a utility operations center and another near an urban center—to model how their storage potential can impact the reliability and cost effectiveness of the northwest electrical grid.  

PGE is piloting several battery-storage projects, including a 5 MW system to measure impact on frequency support and transactive control. PGE is also testing two small systems designed to back up grid power at residential homes during an outage; in non-outage periods that battery systems can be used for grid services. In accordance with Oregon HB 2193, PGE submitted a proposal to implement storage projects totaling up to 39 MW in five different locations. Implementation for these projects could start as early as 2019.

Solar has yet to be adopted in the northwest at the same level as California, Hawaii, and the southwest. However, the Northwest Power and Conservation Council’s Seventh Power Plan, adopted in 2016, found solar PV to be cost-competitive with wind and natural gas resources in our region. According to the Council, approximately 500 MW of solar capacity was built between 2012 and 2017, with 300 MW from utility solar systems.

What to Consider

Like most DR-related technologies, the potential of intermittent energy resources is still being uncovered. The use-cases and value streams of batteries are still being assessed, with demand response representing just one opportunity, alongside factors such as frequency regulation and time-of-use reduction. Better understanding these use-cases can inform utility strategy, influence technology improvements, and ultimately increase the cost effectiveness of this technology. Cost effectiveness also remains a hurdle for solar PV in the northwest, due to limited sunlight during peak demand times and lack of energy-storage systems to store the energy generated by solar PV. Finding new ways to maximize energy storage capabilities and leverage high-potential solar areas in the Pacific Northwest are likely to be questions for the region to consider moving forward.


Make sure to stay tuned for next week's wrap up article to close out the series. Feel like you learned something? Be on the lookout for our poll and let us know!

In case you missed it - check out the week the previous week's articles: 
Week 1: Getting Started with Demand Response and Distributed Energy Resources.
Week 2: Demand Response and Residential Products
Week 3: Demand Response and Agricultural Irrigation

Check out the syllabus here

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