By Michael McIntyre, University of Louisville
Managing demand response (DR) is both a vital task and a significant challenge for utilities around the country as they seek to increase reliability, increase customer satisfaction and avoid the expense of building new generation capacity or activating peaker plants to meet increasing demand.
Utilities are exploring many ways to meet this challenge, and some of the most advanced approaches are taking place at smaller, municipal utilities such as the Glasgow Electric Plant Board (EPB), which serves a community of 14,000 in Kentucky, about 95 miles south of Louisville. The utility’s recent experience with DR projects revealed that a major key to success is to design a system that combines intelligent components with customer-sited, utility-grade storage.
Glasgow has been taking innovative steps for several years to deal with the changing utility environment-an approach the Glasgow EPB team has dubbed “Infotricity.” In addition to striving for greater reliability, the utility has spent considerable effort on shaping utility load, working with a subset of its residential customers.
Because Glasgow EPB also built a municipal broadband network that delivers utility telemetry as well as data and cable TV service in the community, every household today has access to high-speed Internet service and has had a smart meter installed. So it’s easy for the utility to monitor demand and provide information to consumers at peak consumption times to help them know when they should try to control usage. In addition, the Glasgow EPB makes extensive use of social media to communicate with customers during DR events, allowing consumers to retain a significant degree of control over their environment rather than attempting to make all decisions via automation from the utility side.
Most recently, Glasgow EPB undertook a three-year project to take demand response management to the next step.
The initial stages of Glasgow’s “Infotricity” project focused on the installation of more efficient, intelligent home appliances, particularly for high-consumption applications such as hot water. Now the utility is using a portion of a $7.4 million grant to install GE Geospring heat pump hot water heaters in 330 homes in the community, and is outfitting each home with an externally controllable “smart” thermostat for its heating and cooling systems. This was done to make it possible for Glasgow EPB to automatically manage demand by controlling the temperature of hot water as well as the living space, and pre-heating water for storage at low-demand times, or similarly pre-heating or pre-cooling the living space, in effect, treating the home as a battery.
Though these efforts delivered significant load factor improvement at minimal capital cost, it became clear that more improvements could be realized with additional technology to match the DR need, especially for energy-heavy uses like heating, cooling and hot water. While it might suit a utility better if hot water use shifted to later in the evening, it’s tough to convince people not to take a shower in the morning before heading to work, so it is important to control water heating beyond the simplistic operation based on a local in-tank thermostat.
Drastically reducing heating and cooling settings during peak times, and then pre-heating or pre-cooling a home, is another way to address peak demand, but it is necessary to finely tune those temperature adjustments depending on the comfort of the residents. Because part of the Infotricity concept involves peak usage rates (rather than time of day), consumers who didn’t change their usage patterns wound up paying a coincident peak demand charge based on each customer’s contribution to the community peak. The initial phase of the project, therefore, met with some resistance from customers who wanted to save money but, because of their actual needs, couldn’t easily shift usage.
To deal with these issues, the next step in the project was to provide some of the consumers in the sample group with reliable, utility-grade storage at the home. It was important to the effort that the system chosen was both economical to install and provided sophisticated control software for the utility. For this project, Sunverge Energy’s Solar Integration Systems (SIS) met the criteria and have been installed in 44 of the 330 homes which will ultimately be outfitted with new smart appliances.
The Sunverge SIS combines high-capacity battery storage, an inverter and control hardware and software that allow the units to be integrated easily into the customer’s existing electrical installation. It was important that qualified installers could install these easily, that they take up little space on the customer site, and that they be connected at the meter socket, to avoid the complexities associated with tying into the main service panel.
By adding this kind of storage system with utility-side control, an alternative source of power-a virtual power plant, in effect-was created to help further increase load factor for the Glasgow homes. The systems charge via the grid at low-cost, off-peak times and then deliver that power during a demand response event, thus reducing the amount of on-peak energy used during a projected peak. This gives homeowners what they are after-reduced peak demand costs without major change in usage patterns-while providing the Glasgow EPB with significant movement toward its goal of increased load factor.
In fact, the results of the program so far demonstrate significant increases in efficiency and reductions in peak load across all the participating homes.
On the efficiency front, the typical newer home with more energy-efficient construction avoids 1,754 kWh of usage per year. Older homes that were less efficient in the first place are projected to save even more: 1,898 kWh annually. Extending those kinds of efficiencies across the entire community would result in a tremendous increase in the community’s overall load factor and a corresponding reduction in generation assets needed to serve Glasgow.
The results are just as compelling when it comes to peak load reduction. On average, Glasgow deals with 60 DR event days each year, with peak loads lasting some three hours each of those days. Energy-efficient homes saw an average load shed of 2.25 kW. Older homes had a much smaller shed of about 0.81 kW, but for the year that adds up to 26.24 MWh avoided for just 180 homes.
It’s important to understand that these results don’t include the potential benefits of customer-sited renewable generation. While customers of many other utilities may see added benefits by using rooftop photovoltaic solar arrays as an adjunct generation source, for reasons of climate, solar is not as attractive an option for Glasgow.
All the savings, therefore, are a result of the combination of intelligent control of efficient appliances, and storage of grid-delivered power at off-peak times (and rates). In a way, it’s like using off-peak power to drive a pumped-storage hydro system; in this case, the Sunverge devices are making each home into its own nano power plant.
In a region where coal provides about half the available power, this approach to managing peak load can be an important contributor to a greener grid, as well as helping homeowners reduce their electric bills. Intelligence and storage together are what make Infotricity a long-term strategy for dealing with the challenges of modern utilities.
Michael L. McIntyre, Ph.D. is an assistant professor of electrical and computer engineering at the University of Louisville, and serves as a consultant to the Glasgow Electric Plant Board.