Direct Current Microgrids: The Wave of the Future?


Photo courtesy of The Alliance Center

The Climate Crisis and Our Aging Energy Infrastructure

What happens when you combine an aging electrical grid with the increased resilience demands of rapid climate change? You get longer, more destructive power outages. Our continued reliance on fossil fuel and long-distance energy transport for energy production and the power outages associated with our aging grid are putting our health, our economy, and our national security at risk. NASA and NOAA agree that the years 2014, 2015, and 2016 each set new all-time temperature records in a stepwise fashion.1 As our global air temperature warms, so do our oceans, leading to stronger, more frequent and more destructive storms.

2017 was a year of record-breaking natural disasters in the United States, including a trio of hurricanes (Harvey, Mariah, and Irma) with damages over $200 billion.2 The residents of Puerto Rico were largely without power for over six months after hurricanes Mariah and Irma hit in November of 2017. Recent reports3 argue that the storms themselves, combined with the devastation to the island’s energy infrastructure, resulted in over 4,000 casualties. Natural disasters like the hurricanes that pummeled Puerto Rico highlight the risks, inefficiencies and correlations between our changing climate and our aging energy infrastructure.

Our current energy infrastructure is increasingly unstable and underfunded. With more than 640,000 miles of high-voltage transmission lines in the lower 48 states aging out of their 50-year life expectancy, funding gaps in electric generation, transmission and distribution are projected to grow to a level of $107 billion by 2020.4 From the 1950s to the 1980s significant power outages in the United States averaged fewer than five per year.5 In 2011, there were over 300 significant power outages on the grid. Furthermore, while 40 percent4 of new power generation came from natural gas and renewable energy in 2015, our antiquated electrical grid is currently incapable of absorbing all of the energy produced by renewables, meaning a substantial amount of potential renewable power – power that we are capable of producing – cannot be used. What does this mean for our energy security? It means that we can expect longer and more frequent power outages across the country, and that without significant investment, much of the energy generated by that could be produced from renewable sources will be lost because of inefficiencies in the current grid.

 
Eliminating the Middleman: Direct Current Microgrids
The current electrical grid in the United States was instituted at the turn of the 20th century. The grid was developed to deliver alternating current (AC). AC has long been the preferred method of energy transfer as it can be easily transmitted over hundreds of miles. The nation-wide electrical grid operates on AC, which requires inefficient conversions to power modern technologies that operate on direct current (DC). Technologies such as solar panels, computers, cell phones and modern LED lights all operate on DC. As such, we must convert the energy that comes from the AC grid into DC voltage for those devices to function – resulting in at least five to ten percent energy lost6 during conversion. The United States Department of Energy’s Power America initiative predicts that by the year 2030 an estimated 80 percent7 of all US electricity will require conversion from AC to DC, which creates the potential for significant energy savings if conversion can be reduced.
 

Photo courtesy of The Alliance Center
Audience at one of the many programs produced by the Alliance Center for the Denver community

 

What was considered a strength in the past – the fact that AC power can be transmitted hundreds of miles – is quickly becoming a dangerous weakness due to security and resiliency issues. Sabotage of a small section of the grid, or even just destruction due to a natural disaster, can affect customers over a broad area. Furthermore, the dependency on fossil fuels for electricity and heat is the largest single source of greenhouse gas emissions at 25 percent.8 Fortunately, economic, technological, and social forces are uniting to tackle these systematic and embedded challenges.

 
Economic Returns: Why Solar Just Makes Sense

Renewable solar energy is more efficient and cost effective than ever before. 15 years ago, it was projected that the solar market would grow by one gigawatt per year by 2010. By 2015 that projected growth rate was exceeded 53 times over. By 2016, 75 times over. The cost of crystalline silicon solar cells in 2016 was $0.41 per watt.9 In other words, solar photovoltaics are over 150 times10 cheaper now than they were in 1970, while oil is about 35 times more expensive.

While the solar industry is currently under attack by the Trump administration, the local and regional economics of solar power indicate that there is great momentum that forecasts continued growth in the sector. For example, in Colorado, Xcel Energy – an investor-owned utility operating across eight states – recently released the Colorado Energy Plan11 which promises to save the utilities’ customers more than $200 million by shuttering an aging coal plant and replacing it with a combination of renewable energy and battery storage. Aside from saving customers money, this plan has the potential to cut Xcel Energy’s greenhouse gas emissions by 55 percent by 2026. It will take Colorado one step closer toward 100 percent renewable energy.

However, the DC electricity generated by solar must still travel through our aging AC grid to reach consumers. It loses energy as it moves through the grid and is converted from DC to AC, and loses energy again when it is converted back to DC in our homes and businesses to power our personal electronics, lights and other DC native technology.

 
Building Resiliency: Direct Current Technology
By integrating direct current energy from renewable sources into local microgrids, we can eliminate greenhouse gas emissions and greatly reduce the risks associated with our aging national infrastructure. A microgrid is a self-contained electrical distribution network that can disconnect from the traditional utility grid and operate autonomously. The term “DC microgrid” refers to a system of local power generation and distribution in the form of direct current. A DC microgrid can keep key systems operational during power outages or issues with the wider electrical grid. This offers benefits for both short term interruptions, as well as larger scale outages such as natural disasters.

Hurricanes such as Harvey, Mariah and Irma highlight the advantages of local power generation, storage and distribution. As mentioned earlier, those three storms left the residents of Puerto Rico without electricity for months, leading to a much higher death toll in the time after the storms than during the events themselves. While increasing energy demand, threats from cyber hacking and natural disasters will only continue to increase stress on our national grid, DC microgrids offer an uninterrupted local power supply through renewable energy sources and an on-site battery bank. Whether DC microgrids are fed by batteries, generators, fuel cells, photovoltaic panels or small wind turbines, they provide a level of protection and resilience in the face of natural disasters.
 

Photo courtesy of The Alliance Center
The Alliance Center, a former warehouse at 1536 Wynkoop Street in downtown Denver

 

This resiliency benefit can also be calculated as it relates to the economic benefits of a stable and secure workplace. Companies such as Honda are installing DC microgrids at their facilities to reduce the risks associated with power outages including the loss of data, productivity and data insecurity.

 
A Radical Test Bed: The Alliance Center’s DC Microgrid Project
According to the U.S. Energy Information Administration (EIA), in 2012, the building sector (residential and commercial) consumed nearly 75 percent of all electricity produced in the United States. This equates to more than 3 million GWh or 1.7 billion tons of CO2 emitted annually from the building sector alone. If these CO2 emissions were reduced by even seven percent, the result would be the equivalent of removing more than 23 million cars from the road.

In Colorado, The Alliance Center, located in the heart of lower downtown Denver, has become a focal point for producing change of this type and scale. Our mission is to bring people together to create a world where our communities are inclusive, our democracy is strong, our economy thrives and our planet is healthy. We are a multifaceted nonprofit with an event and collaborative working space that we use as a demonstration site for sustainability in action. As one powerful node of our broader sustainability network, we are specifically focused on reducing greenhouse gas emissions, increasing the number and impact of socially and environmentally responsible businesses, and engaging a wide diversity of stakeholders to drive sustainable solutions in Colorado.

The Alliance Center was the first building in Colorado to become certified Platinum in the newest LEED version 4 and the first building in Colorado and fifth in the world to earn LEED ARC certification. With an Energy Star rating of 96 the Alliance Center is one of the most energy-efficient buildings in the state. Our impact programming scales our work beyond the brick and mortar of our building and drives measurable solutions across the Front Range. We convene decision makers and connect communities to drive strategic and inclusive collaboration.

 
Piloting a DC Microgrid in an Existing Building
Since our founding, The Alliance Center has explored ways to reduce the building sector’s contribution to greenhouse gas emissions by serving as a model for high-performance building innovation. Because prices in on-site renewable generation and energy storage continue to fall, and demand for energy continues to rise, we aim to take a fresh look at how we generate, transmit and use power.

At 40,000 square feet, The Alliance Center is within the range that represents 95 percent of the commercial building inventory in the United States. This creates a tremendous opportunity for our own DC Microgrid Project to provide a replicable and scalable model for extreme energy and carbon reduction in the 5.6 million commercial buildings sector – comprising 87 billion square feet of floor space – in the U.S.

The Alliance Center has been modeling energy efficiency and cutting-edge high-performance building practices for over a decade. In 2004, as part of our mission and commitment to sustainability, we converted our building into a highly efficient workspace. Through the renovation, we achieved an Energy Use Intensity (EUI) rating of 37, which is nearly 60 percent lower than the average EUI of 89 for comparable office buildings. We also eliminated all onsite combustion of fossil fuels – removing any instance of natural gas used for heating – meaning that all of the energy used in our building is currently from grid AC electricity.

Despite the success of the transformation in reducing energy consumption, however, we still consume more than 440 megawatt hours (MWh) of grid AC electricity annually – which equates to an annual carbon footprint of approximately 400 tons of greenhouse gas emissions. To take our efforts to the next level, we undertook a revolutionary new project.

In 2017 we installed the equipment that powers our DC Microgrid Project here at The Alliance Center. This equipment includes solar panels on our roof, DC-powered lights in suite 100, and batteries, a rectifier, a combiner and a voltage converter in our basement. Installation was complete at the end of December, 2017.

Our DC Microgrid Project makes it possible for us to take energy directly from an onsite energy generator (25.7 kW of photovoltaic panels) and use onsite storage (84 kWh of batteries) to power portions of our building. While energy from solar panels is typically converted from DC to AC and back again, our microgrid removes this need by replacing our lighting and plug loads with DC-native technology. This eliminates the need for bulky and energy-inefficient converters like the one on your computer cord.

The Alliance Center and our partners are excited to be piloting the DC Microgrid Project as another way for buildings to reduce their negative contribution to climate change. This project has the potential to radically change the energy paradigm for how buildings interact with the grid. While DC microgrids have significant potential, questions remain before they can scale in the commercial building sector. For example, native DC equipment currently comprises over 50 percent of a building’s energy usage, while reported energy savings from DC distribution varies by up to 40 percent. We are piloting DC microgrid technology and collaborating with industry thought leaders like the National Renewable Energy Laboratory to highlight the barriers to and potential of the adoption of DC microgrids in the commercial building sector. We will be testing, learning, adjusting and sharing our lessons along the way, so please follow our progress, learn along with us and get involved.

 
References

    1. Potter, S, Cabbage, M & McCarthy, L. NASA, NOAA data show 2016 warmest year on record globally [online] (2017) https://www.nasa.gov/press-release/nasa-noaa-data-show-2016-warmest-year...
    2. NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters [online] (2018). https://www.ncdc.noaa.gov/billions/
    3. Robles, F. Puerto Rican government acknowledges hurricane death toll of 1,427. The New York Times. [online] (2018) https://www.nytimes.com/2018/08/09/us/puerto-rico-death-toll-maria.html.
    4. American Society of Civil Engineers. 2017 Infrastructure Report Card [online] (2017) https://www.infrastructurereportcard.org/cat-item/energy/.
    5. Davies, D. Aging and Unstable, the nation’s electrical grid is “The Weakest Link”. Fresh Air, National Public Radio [online] (2018) https://www.npr.org/2016/08/22/490932307/aging-and-unstable-the-nations-....
    6. The war of the currents: AC vs DC power [online] (2016) www.energy.gov/articles/war-currents-ac-vs-dc-power.
    7. Power America [online] www.energy.gov/ecre/amo/power-america
    8. IPCC. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. (2014)
    9. New Energy Outlook 2018 [online] www.about.bnef.com/new-energy-outlook/toc-download
    10. Seba, T. Clean Disruption of Energy and Transportation: How Silicon Valley will make oil, nuclear, gas, coal obsolete by 2030. (2014)
    11. Svaldi, A. Xcel Energy power plan would cut carbon emissions by half, use renewable sources for 55 percent of power. The Denver Post. [online] (2018) https://www.denverpost.com/2018/06/06/xcel-energy-power-plan-would-cut-c...

 
Acknowledgements
The author would like to thank Chris Bowyer, Moira Wiedenman, Jason Page, and Brenna Simmons-St.Onge for their help reviewing and compiling the data and narrative for this article.