These days you can’t turn on the television, log on to any social media website, or check your Twitter feed without seeing something about climate change, fossil fuels, renewable energy, sustainability, and energy efficiency. Regardless of your political orientation, the reality is that we all should have a goal to become more energy efficient.
As engineers, we all want to better the world by reducing our carbon footprint and energy consumption while providing resiliency in an ever-changing world. We work hard to integrate renewable technologies in our system designs, and try to address man-made and natural disasters.
In this world of ever-changing technology, one of the recent “it” topics is microgrids. It seems like everyone is jumping on to the microgrid bandwagon. As an electrical engineer, I am interested in this topic from the aspect of understanding the ability to utilize multiple energy sources to create a resilient and sustainable power source. As a code nerd, I am also interested in how the concept of a microgrid interfaces with various code requirements for emergency back-up power. Also, as a health care electrical engineer, I am interested in looking at the feasibility of utilizing a microgrid for various types of health care facilities.
Because the concept of a microgrid is still relatively new, there is a lot of misinformation floating around about what it actually is and how it can be utilized for a facility. One of the definitions I have heard regarding a microgrid equates to “island power” or a solution to the desired “resiliency” required to sustain a facility upon a power outage. This interpretation misrepresents a resilient infrastructure as a microgrid, when in reality a microgrid is a more complex design intended not only to provide resiliency, but also sustainability and potential financial benefit to a facility, campus, or complex.
The U.S. Department of Energy Migrogrid Exchange group provides the following definition of a microgrid:
“A microgrid is a group of interconnected loads and distributed energy resources (DERs) within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.”
This gives a basic context, but really doesn’t help define the components or the implementation. When you look at the definition of Distributed Energy Resources (DERs), a DER is not limited to energy production and storage sources but also includes demand management. This is where you start to see the differences between a resilient design and a microgrid.
Typically, the energy production methods for the DERs are renewable or alternative energy systems including biomass, combined heat and power (CHP), solar, wind, and geothermal sources with the storage systems primarily batteries. Understanding the power and storage source options is the simple part. It is the demand management component that transforms a resilient design to a microgrid. The demand management program looks at all of the available energy sources and balances demand versus the available resources. If a portion of the microgrid is comprised of solar and wind energy, it isn’t realistic to assume that these sources will always be available and have a consistent power output. The sun doesn’t always shine, and the wind doesn’t always blow. This is where the demand management programming will evaluate what energy is available, what is available from the associated storage system, and what is available from either other on-site power resources or from the utility grid. The management of the system is consistently evaluating the energy systems, and it is not a static process. This is the biggest differentiator between a microgrid and island power.
Now let’s think a bit about code requirements. A health care facility is required by NFPA 70, 99, and 110 to have an emergency backup system. Depending on the type of health care facility the requirements differ, but a consistent requirement is that the essential systems require two separate sources of power. A logical question for this requirement would be “why do I need a backup power source if I have such diversified energy sources and associated programmed controls for my microgrid system?” I agree with the fact that a microgrid provides resiliency from a power source perspective, but what happens if the distribution equipment for the microgrid fails? Where is the second “separate” source of power? The purpose of an essential systems distribution is not just for the source of power but also the path the power travels. By relying only on a microgrid system there is still a single point of failure somewhere within the system near the primary distribution source — even if there are multiple sources of reliable power available. So if you have a health care facility that utilizes a microgrid design, the code still requires that you have to have an emergency backup system that is separate from the “normal power” source.
Looking at the design requirements for a microgrid, in conjunction with the general code requirements for essential systems, is it realistic to utilize this type of a technology for health care facilities? Before I provide my opinion on this topic, I do want to reiterate that it is important to evaluate and invest in sustainable and renewable resources for power sources. (I don’t want the sustainability police at my desk.) As we progress with technology and innovative power options, resilient systems will consist of more than the traditional utility source and diesel generator backup, and we need to be ready to respond to these demands. So, with all of those disclaimers, I am now going to put on my health care design engineer hat. With more than 25 years of design experience, I have worked on projects ranging from a simple single room remodel to a critical access hospital to a health care campus and everything in between. Full disclosure: I am also married to a construction manager, which allows me to understand the financial side of the construction process in greater detail (sometimes more than I would care to acknowledge).
Because of my health care design experience, and understanding where priorities are with the need to procure funding for projects to address clinical needs, I am going to go out on a limb here and say that an investment in a microgrid is not always the right choice for all types of health care facilities. This does not mean that alternative energy sources are not a good choice for a health care facility though. If the health care facility is part of a larger campus system, it may be feasible to look into these alternate technologies in a microgrid scenario. It is necessary to not only look at the resiliency aspect but also to evaluate if the payback and the savings from the utility are financial responsible. It is also important to understand if there is an entity that will be able to implement and maintain the system. Health care facilities staff is already overworked and typically do not have enough FTEs to address current needs, let alone run and maintain a plethora of energy-producing equipment. The reality is that not all facilities would benefit from a microgrid design.
Before you start rebutting my opinions that a microgrid is not (currently) the right solution for all facilities, please be mindful that a microgrid is not equivalent to a resilient infrastructure. A microgrid is resilient, but resiliency is not necessarily a microgrid. This doesn’t mean that a resilient system isn’t a good choice for a smaller health care facility or a facility that is at risk for a natural disaster or desires additional redundancy in the event that there is an event with the utility grid. In fact, I am in favor of “island power,” as long it is assessed to be necessary to address the risk and is able to be sustained by the budget and the facility.
So, after evaluating all of the factors and priorities that impact a power distribution design, let’s say we determine that a microgrid is a good solution. It’s now time to remember a few things to assure compliance with codes. As noted earlier, a separate essential systems distribution is still required to be included in the design. The codes do provide some flexibility regarding what constitutes a “reliable” source of power to be utilized for the essential systems beyond a traditional diesel generator. If an alternate energy source, or new emerging technologies, is not already incorporated into the current codes as approved sources, the design solution would need to be approved by the AHJ prior to implementation. The design of the essential systems would need to be clearly thought through so it could be incorporated into the microgrid scenario and not compromise the efficiency of the grid or the safety of the essential systems distribution.
Whenever there is an interface with the utility grid, it is crucial to include the impacted utility in the design discussions. Some utilities will provide financial incentives to create a microgrid application but some also may be hesitant to embrace the design. Not only are there concerns about power quality returning to the grid, but also think about what happens when you run into a cloudy day without any wind, and you have exceeded the duration of your energy storage units. Where does the power come from to serve your facility? The demand on the utility may not be easily accommodated on short notice, so open discussions with the utility are crucial. The full impact microgrids have on the utility grid is a topic for another day with a few more experts to share how this decision impacts their faction of the power distribution industry.
Typically, when I write these articles, I like to share my knowledge of a particular code requirement or design scenario. The intent of this particular article though is to clear up the fact that a resilient electrical distribution design is not necessarily a microgrid — and that there are many factors that are required to be taken into consideration before one goes down a microgrid path, particularly for a health care facility. Some of you have commented in my previous articles, and I would welcome your thoughts on this article regarding the misinterpretations (or misuse) of the term microgrid — and how you see a microgrid design being implemented for health care facility now or in the future.
