dc power microgrids

So many striking changes are taking place in the modernization of the electric power grid that it’s easy to lose the forest for the trees. However, I’d actually like to take a closer look at some trees: the needs of individual customers, particularly those impacted by repeated, prolonged grid outages.

I’ve had many conversations over the past several months about customers’ growing dissatisfaction with the energy and service that they receive from the grid as well as the growing number of supplements or outright alternatives to the grid that they are being offered by disintermediaries. Customer dissatisfaction arises from a variety of sources including rising prices, unacceptable environmental impacts, complex pricing schemes and demand response programs and inadequate customer service and communications. In the wake of increasingly frequent severe weather events (e.g., Hurricane Sandy, derechos, Oklahoma tornadoes, California wild fires, etc.) and the looming threats of inadequate generation resources during yearly peak load periods, customers are ever more concerned about the increasing frequency and duration of service outages. More residential, commercial and industrial customers are asking, “What can I do to supplement or even substitute for the energy that I receive from the grid?”

In my previous post I mentioned the concept of a subsystem for the home or business that is DC rather than AC. This would involve increasingly available and affordable distributed DC generation sources, including solar photovoltaic cells, fuel cells and battery storage. It would also include end-use devices that operate on DC.

Historically the major customer load categories have all been designed and wired for AC:

• Lighting

• Residential appliances/commercial and industrial machines and equipment

• Residential/commercial water heating/industrial process heating

• Residential and commercial refrigeration and air conditioning/industrial refrigeration

• Space heating.

So, DC will not be a complete solution for customer energy independence in the near future. However, a rapidly increasing portion of energy consumption, particularly for residential but also for commercial and industrial customers, is made up of electronic devices (see How Small Devices are Having a Big Impact on U.S. Utility Bills) which are designed to operate solely on DC. Today that DC power comes from AC to DC conversion at each end-use device or to supply multiple DC devices in a DC subsystem.

Customers have questions about how to cope when the grid goes down, especially for an extended period. Should they buy a backup generator capable of powering their entire needs? (E.g., like has already been implemented by many homeowners, commercial data centers, strategic military facilities and telecommunications networks.) Or is only a subset of loads critical to maintain? What can they get by without? How would they best meet their minimum electricity needs in an extended outage?

The essential question is “how a customer can maintain the minimum critical subset of the premises to ensure safety, security and the need for information and communications when the grid is down?” Interestingly enough, some residential customers get into their own DC microgrid, their vehicle, which provides shelter, HVAC, light and the ability to charge up their computers and phones and tablets, even the ability to go find power in another grid that is not out of service. And their microgrid has its own DC generation and storage! In the event of a national disaster or threat, the President of the United States boards Air Force One – an airborne DC microgrid!

Many customers will likely tend to choose electronics first, even before lighting or the refrigerator because of their need for information and communications – computers, mobile handheld communications devices, Internet routers, radios and TVs (and electronic cameras so they can upload images for friends and family at Pinterest and Vine). These are all DC loads although today they run on AC converted to DC by “wall warts” or internal AC to DC rectifiers. After the DC-consuming electronics, what are the other essentials? Lighting? Most customers’ backup lighting is already DC, powered by batteries. And essentially all lighting could eventually be DC. Cooking, water heating, space heating? If it’s electric, it’s primarily resistance heat that could eventually be DC powered. Refrigeration, central air conditioning, heat pumps and other motor-driven devices require AC, but DC motors could work just as well.

If an adequately accessible and affordable alternative is available, residential customers will add comfort, convenience and entertainment while C&I customers will choose to restart business operations. And, even in the ideal, unattainable scenario in which the grid never fails, customers might run their backup system or subsystem to reduce their utility bill or reduce their carbon footprint or improve energy sustainability.

These are grassroots, individual needs, but they have big implications. The ability to make a stand, as it were, during grid failure, could help stabilize a community under duress from natural disaster (i.e., reduce panic, avoid civil disorder, allow the most effective triage of emergency services). I can foresee companies that now install solar PV or fuel cells or battery backup also offering or partnering with companies that offer affordable DC subsystems that includes the retrofitted wiring, maybe even battery storage. Systems sized for such minimal, disaster recovery purposes could make them more affordable than one designed for the entire premise’s load.

As systems like this achieve grid parity (i.e., the cost/benefit is acceptable to the customer compared to utility service), the market will be substantial. And grid parity isn’t just cost. It may be reliability or sustainability or carbon footprint or plain old Ayn Rand-style independence from “the system.” As legacy, grid-supplied energy increases in cost, decreases in reliability, causes unacceptable environmental impacts and has inadequate customer service and communications – and as disintermediaries offer better alternatives – “edge power” solutions will proliferate.

I suspect thousands if not millions of people affected by Hurricane Sandy would have moved on such an option in the months after the disaster, while it was fresh in memory and emotion. That kind of urgency fades over time, but the Northeast had two or three such events in rapid succession in the past few years and the likelihood of recurrence surely would motivate a significant number of people to pursue an affordable solution. Early adopters who weather a natural or man-made disaster in this manner could provide solid performance data. By the way, think of the value such an approach has in emerging economies or isolated communities without access to grid infrastructure. 

The U.S. military is already experimenting with microgrids of this sort for mission critical facilities. They recently announced the concept of a “decision making” microgrid that has benefits that go well beyond emergency backup power, including automatically choosing various degrees of grid dependence. See Microgrid Means Mega Advantage.

Think about how this will affect utilities. Most utilities see only bad news: reduced energy sales cause reduced revenues while not reducing costs, resulting in higher rates to customers. Higher rates to customers in turn increases adoption of the “off the grid” solutions. Utilities that have a strong commitment to efficiency, sustainability and environmental protection (or whose legislators and regulators force them to) will find increasingly self-sufficient customers to be a godsend. So will utilities who find it technically, economically or institutionally infeasible to add central station generation or new bulk transmission facilities. Quasi-grid independent customers will also be of benefit to utilities when their nanogrids or microgrids are operated in such a way as to enable the grid to accept more renewable energy from wind, solar PV and other renewable sources.

In short, depending on how such a scenario played out, a movement toward mass adoption of DC subsystems could definitely help consumers and might help or hurt utilities. The market will be driven by need and the cost/benefit ratio for customers, not their utilities. The customers foot the bill for grid outages anyway, both theirs and their utility’s. Why not invest some of that money on some measure of self-sufficiency? That’s going to be a trend worth watching, by citizens and utilities alike.