DC Microgrids

6610b-austinBy Austin Good | Sustainable Building Associate

The Institute for the Built Environment (IBE), in partnership with the Center for Energy and Behavior, the Energy Institute, Positive Energies (PosEn), the Colorado Clean Energy Cluster (CCEC), and Schneider Electric have come together to research the use and benefits of DC microgrids. The proposed collaboration includes construction of a new DC microgrid laboratory facility at CSU’s PowerHouse Energy campus and the initiation of new research directions in social science, built environments and DC microgrids.


What is AC & DC Power?

There are two types of electricity, Alternating Current (AC) and Direct Current (DC). These two types of electricity describe the types of electric current that flow through circuits. Each type of current has benefits and limitations. AC power, the power that flows through our current power grid, was chosen as the main form of electricity over 100 years ago. AC became the current of choice because of the ability to transmit power long distances without losing much energy to heat.  AC power is also able to be transmitted at high voltages then put through a transformer to reduce the voltage for the end use of the customer. DC voltage on the other hand cannot be scaled and was much more costly to transmit over distances.

Why DC power?

So why are we talking about DC power? AC power is becoming extremely inefficient for today’s uses. Our world has moved toward increasingly higher uses of semiconductors. Semiconductors are essential components in the electric circuits many devices, including computers, smartphones, televisions, and electric vehicles.  And semiconductors require the use of DC power. Because the power coming into our homes and offices is in the form of AC, conversion is required. During this conversion excessive power is lost to heat making conversion inefficient.

This problem is becoming more pragmatic today as people begin to generate their own power close to home through solar or other renewable means. These renewable sources output electricity in the form of DC power. However, because of the way our infrastructure is built, the power generated by renewables must be converted to AC power, transmitted through the current power grid, and then converted back to DC power within the device that is using the electricity, making the power subject to two inefficient conversions before reaching its end use.

emergediagram

Via recool.com

Enter DC microgrids. The idea behind DC microgrids is that we can begin embracing power that is generated nearby instead of the power generated at far away central power plants. These DC microgrids could optimize our systems to accept DC power directly, from generation to use, without going through two conversions. Other DC microgrid projects have demonstrated energy savings in the double digits, ranging from 10%-42% (Nextek Power 2010). One such system, called a MEG (Modular Electric Generator), is a truly next-generation DC power generation and distribution system. By coupling sources and loads using DC, the MEG improves efficiency and reduces the cost and complexity of power conversion systems. It utilizes PV power generation and battery storage to reduce grid coupling to an absolute minimum.

What is IBE studying?

Studies on green building technologies have identified three primary barriers to the adoption of innovative strategies: individual, organizational, and institutional (Hoffman and Henn 2008).  Additionally, many promising energy technologies, including DC microgrids, are not scalable. Initial user reactions and/or slow adoption prevent technical solutions from achieving their design goals. For example, often times building owners and clients are not aware of up-to-date research or the potential benefits of deploying these systems at scale. When it comes to DC microgrids, user expectations, building codes, and utility interconnections have been identified as the primary barriers to widespread adoption.

This study aims to understand barriers to the adoption of DC power systems in commercial buildings by creating an interdisciplinary team of academics, practitioners, industry professionals, and non-profit leaders to examine the technical issues and social barriers. The research that IBE conducts will be done in concert with the development of new laboratory facilities at the CSU Powerhouse Campus, which will test a MEG DC microgrid system. The resulting white paper will provide valuable information on the development, deployment, and acceptance of large scale DC microgrid technologies.

References

Fortenbery, B., EPRI, E. C., & Tschudi, W. (2008). DC power for improved data center efficiency.

Hoffman, A. J. and R. Henn (2008). “Overcoming the social and psychological barriers to green building.” Organization & Environment 21(4): 390.

Nextek Power. “AC vs DC Power?” YouTube. YouTube, 15 Sept. 2010. Web. 30 Aug. 2015.

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