Microgrids: meeting grid and customer needs in the US
Microgrids: meeting grid and customer needs in the US
Introduction: responding to the triple threat
This triple threat calls for looking beyond the usual suspects. We need alternatives to expanding and upgrading the grid’s transmission system as the only solution to what ails it, along with improvements that complement the current approach of central power generation sources. Transmission system expansion and upgrade projects are huge, take years to achieve, and “Not-In-My-Backyard” (NIMBY) opponents are major stumbling blocks to deploying additional transmission capacity when needed. Finally, increased demands from electrification for heating and transportation will require a solution to improve to the electrical infrastructure and mitigate outage risks.
A microgrid might be one solution. To understand what a microgrid is and how it fits with our current grid, a brief explanation of what our current grid is will be helpful.
The existing US grid Our current electric grid in the US includes all the electrical generating facilities, together with the lines that connect them to all the end users of electricity. Those connections are via an extensive system of high voltage transmission lines from those generating sites, supplying local distribution lines that in turn supply the customers, along with considerable ancillary equipment such as transformers, protective devices such as fuses and circuit breakers, switches and system monitoring/control equipment. When parts of the grid and or its many interconnections are disrupted or fail, an electric outage may occur, which can affect either a few electricity customers or an entire region, across all customer classes -residential, commercial and industrial.
A definition for the terms Resiliency and Reliability, which are not the same:
Resiliency is the ability to withstand or recover from an adverse condition, deliberate or accidental.Reliability is a measure of a system to perform over time without failure.
But what if those risks were to be spread out more from the existing central station and transmission model - i.e. lots of baskets with fewer eggs? Perhaps it is time to include microgrids in the toolbox to address these issues and support the current administration's infrastructure improvement plans.
Local energy pods Think of microgrids as local energy pods which might serve one user, or one neighborhood. Its simplest definition would be a local energy grid, normally working while connected to the existing, larger grid, with local control and generation supporting some amount of the local microgrid’s electrical loads. This would support the grid in relieving transmission congestion by displacing power load which otherwise could be provided from the grid; it would also be able to be disconnected from the grid through manual or automatic switching. Operating while disconnected from the main grid is referred to as islanding; this operating mode can also improve grid resilience, as it relieves potential grid disturbances which might otherwise result in an interruption of supply.
Autonomous operation Operating autonomously from the main grid allows microgrid customers to continue to operate at some capacity during emergencies, or during a power outage. While microgrids might not necessarily provide their customers with their total electrical demand, it can help avoid losses that might occur with the loss of critical power, such as food spoilage from loss of refrigeration, maintain electricity to industrial process safety controls, or putting people with medical conditions at risk, including those who rely on home oxygen supply machines, or who are susceptible to temperature extremes stress due to loss of air conditioning or heating.
Relieving demand stress Other microgrid benefits include relieving the grid of demand stress, such as during a heatwave. That displaced electric demand could then be provided to other main grid customers during high demand times that might have otherwise been unable to be provided. One recent example from last year’s headlines occurred in California in 2020, when a heatwave combined with rolling blackouts to address wildfire concerns left many customers without power; a microgrid may have mitigated that impact. An electrical load that is able to voluntarily disconnect from the grid when requested by a grid operator during periods of high demand is referred to as a “demand resource”. By displacing some electrical load, the grid stress is relieved for use by others and the need additional generation might be avoided. A demand resource is often revenue source for the customer(s) who disconnect in support of the grid.
Supporting the energy transition Microgrids also support the expansion of renewable energy, with the use of solar photovoltaic systems, a frequent choice which contributes to the increased use of greener forms of energy, typically paired with a battery energy storage system (BESS). A BESS is necessary for grid tied solar PV systems in the microgrid to provide backup power to the microgrid when it goes down and/or operates in islanding mode, as well as providing backup for the microgrid when the sun is not shining. A BESS can also provide other benefits to microgrid customers, including generating revenue for the microgrid in supporting the main grid.
Reducing T&D losses As mentioned earlier, the reduced demand on the main grid system helps reduce energy losses in the transmission and distribution (T&D) system, improving the overall efficiency of the main supply. Lower losses in T&D can result in lower greenhouse gasses from conventional fossil fueled generating plants.
Microgrids have been identified as a key component of the Smart Grid for improving power reliability and quality, increasing system energy efficiency and providing the possibility of grid-independence to individual end-user sites1 , especially during main grid interruptions.
A microgrid system can include multiple generation sources, such as Solar PV, Fuel Cells, BESS and Wind (in some cases) and usually backed up with emergency generators fueled with natural gas or diesel fuel.
While a microgrid system is not necessarily a completely green solution, it can often have green attributes. Where economical, it can include heating or cooling options as well, capturing waste heat from an engine driven generator. This would benefit system efficiency, lower costs to customers for electricity from the microgrid as well as lower demand charges from the utility grid supplier. In some cases, this may result in lower overall emissions compared to the normal grid configuration.
Improving resilience Microgrid systems can improve resiliency by responding to grid failures and rolling blackouts due to wildfire concerns, as well as adding supply reliability. Furthermore, as an additional benefit the load displaced from the grid would delay the need to expand grid capacity. This might provide a motivation to work on a solution to address California’s recent rolling blackouts in 2020, which were initiated to mitigate wildfires that might be caused by live electrical lines. The California Public Utilities Commission is funding a microgrid plan to assist communities to build microgrids as the first step in improving the resiliency of the power supply for electrical customers as wildfire threats show no signs of abating.
In January 2021 greentech.com published an article entitled: “California Sets $200M Budget for ‘Complex, Multi-Property Microgrid’ Projects”. In it they stated:
“California regulators have approved a microgrid plan3 directing $200 million to help communities build networks that can supply power through the state’s extended wildfire-prevention blackouts, a task expected to take years to move from planning to completing its first projects.”4
Elimination of electrical losses A secondary benefit of having generation near the load is that it eliminates the electrical losses that occur over long transmission lines and local distribution lines in the conventional grid systems. This would be a shift from the current system of central station power supplier, and relieve capacity on existing grids, but would not necessarily do away with the need for either. However, it would free up capacity on existing grids to supply new loads elsewhere without new transmission lines.
Addressing soaring electric demand Electrification refers to the transition from fossil fuel energy to electrical energy. In the US, the transition to electrification includes the expectation that electric demand will increase significantly, further stressing the current grid. The US National Renewable Energy Laboratory (NREL) predicts that to meet the electricity demand in high electrification scenarios, installed electric capacity will grow to double the 2018 levels by 20505 .
Transportation, primarily in the form of electric vehicles (EV), together with conversions of space heating from gas and oil to electric heating, will create a need for additional electric power generation and grid capacity to meet this demand. It is predicted that the by 2030, EV charging requirements alone will increase grid demand by 25-30%6 . The planning needs to be done in advance to be ready for that increased demand when it comes.
Microgrids are well positioned to contribute to this transition, for the reasons mentioned earlier, including relieving demands on the existing grid and help support the varied and flexible load demands of EV charging.
Other suitable microgrid candidates Microgrid projects can be suitable for communities, public institutions and college campuses, military bases, growing for military bases, airports and small communities/commercial sites. A few examples of microgrid projects planned or in service include:
The City of Gonzales, CA is developing a 335 MW microgrid at a cost of $70 million. The microgrid will have 80% of its power from renewable energy (primarily solar PV panels, and a BESS) and about 20% from natural gas fueled generators. A key driver for this project is the past and future expected power shutoffs to prevent wildfires. Furthermore, the Zocalo website reported on February 16 2021, in an article entitled “The Huge Electric Leadership Of A Small California Town”:“And PG&E’s use of regional power shutoffs to prevent fires has made finding local power sources that won’t shut down even more urgent. During one 2019 shutoff, Gonzales lost power for two days, resulting in multimillion-dollar losses for local employers. This month, a PG&E lawyer said that these intentional outages will continue indefinitely.7 8 ” Miramar Marine Corps Air Station, which is developing a microgrid powered by solar, landfill gas, natural gas, and diesel fuel. Key goals of the microgrid include resiliency (they lost power previously), and it will allow for peak shaving to save demand charges from its utility supplier9 .
Conclusion: the case for microgrids
1 The Electricity Journal, The U.S. Department of Energy’s Microgrid Initiative, October 2012, Vol. 25, Issue 8 Published by Elsevier Inc. https://www.energy.gov/sites/prod/files/2016/06/f32/The%20US%20Department%20of%20Energy%27s%20Microgrid%20Initiative.pdf 2 US DOE, NREL Voices of Experience Microgrids For Resiliency, November 2020 https://www.smartgrid.gov/files/documents/NREL_VOE-MicrogridofResiliency_Report_Digital-012821.pdf 3 https://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M360/K370/360370887.PDF 4 https://www.greentechmedia.com/articles/read/california-sets-200m-budget-for-complex-multi-property-microgrid-projects#:~:text=The%20microgrid%20incentive%20program%20approved,%2C%20multi-property%20microgrids.%E2%80%9D 5 NREL, Latest Electrification Futures Study Report Explores How U.S. Power System Could Evolve With Widespread Electrification, January 12, 2020, https://www.nrel.gov/news/program/2021/latest-electrification-futures-study-report-explores-how-the-supply-side-of-the-us-power-system-could-evolve.html 6 Power Magazine, March 2, 2020, Driving Change on the Grid-The Impact of EV Adoption, by Darrell Proctor, https://www.powermag.com/driving-change-on-the-grid-the-impact-of-ev-adoption/
