Icing Down the Grid
Southern California utilities send heat packing with distributed storage.
On hot summer days—just when it’s needed most—to cover demand for air conditioning, electricity clocks its highest costs. Once considered a luxury affording comfort and status, that cooling has now become an integral component of our modern infrastructure by keeping us comfortable where we work, shop, and play, while keeping the digital fabric of our communities humming by regulating the temperature for climate-sensitive equipment in data centers and telecom hubs.
Although electric utilities have assets at their disposal, such as gas-powered turbines, to ramp up power to meet peak demand, David Walden, of the Southern California Public Power Authority (SCPPA) says, “The units that we typically dispatch within the industry to meet that peak period are the most inefficient units that we have.”
California’s Public Utility Commission’s summer 2009 report stated that, “because air-conditioning loads drive peak demand, California sees its greatest demand spikes during the summer months” (June, July, August, and September). On a hot summer day, the swing between off-peak overnight demand and on-peak demand during the day can be 85–90%. And according to the report, “the difference in demand between an average summer day and a very hot peak day is 6%.” This difference, the report says, “Is equivalent to three years’ average growth in statewide electricity demand.”
Peak loads also exacerbate inefficiencies in power transmission systems and push generation, transformers, and other energy infrastructure components to their limit and sometimes beyond, threatening both the quality and availability of electrical power to meet essential needs.
However, simply adding more capacity to the supply side of the grid will not solve the problem. According to Greg Tropsa, cofounder and executive vice president of Ice Energy, building power capacity to peak demand has already saddled utilities and the communities they serve with huge inventories of “stranded assets.”
For example, Tropsa says the asset utilization rate in New Jersey is around 47%, “which means that everything they own is only used 47% of the hours during the year; the rest of the time, they are waiting for the next heat wave to hit them.” With concerns over climate change, pollution, and energy security mounting, public policy also mitigates against merely expanding generating capacity to keep pace with ever-rising levels of peak demand. In California, utilities currently face a mandate under California statute AB 2021 to “capture all available cost-effective efficiencies.”
Tropsa says building to peak load capacity that only gets used a small number of hours during the hottest days of summer is far from efficient. Furthermore, he says, “It’s very costly to ratepayers,” whose utility bills subsidize infrastructure that very rarely gets used.
And Chris Hickman, independent consultant and former senior vice president of Utility Solutions for Ice Energy, says that as more and more households turn to air-conditioning during the summer months, “demand on the grid is getting spikier and spikier.”
A Zero-Inventory Commodity
Although electricity cannot be stockpiled and warehoused to meet spikes in demand during heat waves, utilities are nonetheless obliged to supply power at consistent quality whenever customers demand it.
For that reason, Tropsa says, the electricity market is “the only market in the world that has to build to the instantaneous demand of its customers. It doesn’t have storage. Whether you look at gas or any commodity market, storage is there to smooth out the spikes in demand and to insure that there is a reliable supply in case of long-term high demand.”
Walden says, “Anything we can do to reduce demand helps in two ways, by lowering total consumption and improving the efficiency of the system.” He believes storage can play a role in protecting the integrity of the grid by helping to reduce peak demand.
In January, SCPPA signed an agreement with Ice Energy, a Windsor, CO, technology firm, to smooth out spikes in customer demand by powering air conditioners with ice made overnight.
SCPPA is a joint powers authority consisting of 10 municipal utilities and one irrigation district, serving two million customers in southern California. Its members include the municipal utilities of the cities of Anaheim, Azusa, Banning, Burbank, Cerritos, Colton, Glendale, Los Angeles, Pasadena, Riverside, Vernon, and the Imperial Irrigation District. The authority’s plans to deploy 1,500 individual energy storage units on customer premises to reduce peak demand by cooling them with ice during the day, represents the nation’s largest utility scale distributed thermal storage project to date.
In a press release announcing the agreement, Bill Carnahan, executive director of SCPPA, says, “By using storage to change how—and more importantly when—energy is consumed by air conditioning, we can offset enough peak demand in the region to serve the equivalent of 10,000 homes.”
Ice Energy calls the storage units Ice Bears, and the company says the devices are compatible with 85% of air conditioners, ranging from a 3–5 ton system to 20-ton systems. “When we put Ice Bears out on buildings, we’re shaving the peak and filling the trough; we’re isolating the building—insulating that temperature effect on the grid,” says Tropsa.
“Usually, when you’re talking about distributed energy, you’re talking about combined heat and power,” he adds.
And, he says, distributed CHP installations face “very high hurdles” when it comes to getting “installed, financed, and permitted; and that’s why the market has struggled for a long time.
“You have to isolate it; you’ve got to deal with power quality, so you have to have very good controls—good inverters,” continues Tropsa. “The emissions sources, and noise sources— all these things have to be permitted.”
Tropsa explains that power stored in the form of ice is safe. “If we put 63 gigawatt-hours of stored energy on buildings, if a distribution wire goes down, if an electrician has to go and work on the building, there’s no possibility of a shock, or of corrupting electrical equipment on the customer side of the meter.”
Working the Late Shift
Ice Energy says its Ice Bear energy storage system works with a standard commercial air-conditioning system and requires no modification to existing ductwork. The unit operates in two basic modes, Ice Cooling and Ice Charging, to store cooling energy at night and to deliver that energy the following day.
During Ice Charge mode, a self-contained charging system freezes 450 gallons of water in the Ice Bear’s insulated tank by pumping refrigerant through a configuration of copper coils within it. The water that surrounds these coils freezes and turns to ice. The condensing unit then turns off, and the ice is stored until it is needed for cooling.
As daytime temperatures rise, the power consumption of air conditioning rises along with it, pushing the grid to peak demand levels. During this peak window, typically from noon to 6 p.m., the unit switches to Ice Cooling mode and coolant is cycled through the block of ice in the Ice Bear unit, bypassing the air conditioner’s energy hungry compressor, which can be shut down at that time to save energy during the hottest hours of the day.
Once the ice has fully melted, the Ice Bear transfers the job of cooling back to the building’s air-conditioning unit, to provide cooling, as needed, until the next day. During the cool of the night, the Ice Charge mode is activated, and the entire cycle begins again.
To avoid spikes on the grid, Tropsa says the Ice Bear charges over a period of 10 hours during the night—“when there’s just nothing happening; we’re all asleep, and businesses are shut down. The Ice Bear is out there, and it just trickle charges. Then, at the peak of the day, that six-hour rush—when it’s hot out, and shoppers are in the stores, and people are cranking their air conditioners—that’s when we dump the energy.”
According to Hickman, the 450 gallons of ice stored overnight “guarantees six hours of offset to an air-conditioning ventilation system running at full tilt.”
However, he says, on a day when temperatures are less severe, when the air conditioning is cycling on and off, the ice might last considerably longer. But either way, he says, “no longer is the air-conditioning load rising with temperature.”
Instead, with the Ice Bear installed, the demand curve for cooling flattens out at 300 watts to resemble that of a light switch. “It doesn’t matter if it’s 80 degrees outside or 140 degrees outside, it’s only going to be consuming 300 watts to produce that cooling during that time period,” adds Hickman.
A New Business Model
Tropsa says because of the way energy markets are currently structured in the United States, the benefits of load shifting accrue to the utility rather than to individual property owners. “The question is how to get the office building owner to invest in energy storage equipment when all the benefits go back to the utility.”
“We looked at lots of traditional business models like energy service performance contracting, where you look at the utility rate, bundle it with other pieces of equipment, and enter into a contract with the customer,” he states. “That’s great, but our vision was much larger, to transform the utility industry and actually compete with large central power plants like the GE LM 6000 simple cycle peakers and things like that.”
Although Tropsa believes energy markets will eventually move towards real-time pricing, “which means that commercial building owners could be exposed to higher rates during the peak of the summer day,” he says, “energy storage, itself, is a relatively high fixed-cost, long-life, low-variable cost asset,” and “not something everyone can sell knocking on doors.”
“It really becomes an issue about financing and repaying that financing,” he adds. “And that’s what utilities do; they finance large power plants, large transmission, and distribution projects.”
Keeping Up Appearances
Working with energy systems software giant, OSIsoft LLC, as their premier partner, Ice Energy developed a proprietary control system called the Cool Data architecture, which allows customers to not only monitor the Ice Bear units they have installed in the field, but also to control their operation from a central location. Furthermore, Tropsa says the architecture is designed to aggregate the distributed capacity of the Ice Bear units into what appears, to the utility, to be a central resource that they can dispatch as needed.
Hickman explains that the Cool Data architecture allows the utility to control individual Ice Bear units, or to group the devices together in any configuration desired for in tandem control, whether within a single site or across multiple installations.
Hickman says utilities recognize the value of this aggregated asset “as equal to other central generation resources for its capacity value and its energy value. The utility doesn’t care whether it’s one Ice Bear or 10; what they want to know about is the 63 gigawatt-hours of energy that we’re delivering, and the capacity that we have.”
“The secret is to make it feel like something they understand—like a power plant, a small reciprocating engine, or something that looks and feels the same,” says Tropsa.
According to Walden, signing up for the program is relatively simple, the SCPPA does “all the installation,” he says. Customers need only “provide an access agreement as with any other piece of utility equipment, such as a transformer or meter.”
Tropsa says Ice Bear is very complimentary with emerging renewable energy sources, such as building-integrated Photovoltaic and wind power. The company also sees opportunities in helping to enable growth in renewable energy.
“In Canada, what’s happening on the grid is that, because of the large penetration of central wind, they are getting excess generation or surplus-base-load generation available on the grid,” says Tropsa. “So, they’re looking to bring resources that consume energy onto the grid at night.”
Tropsa also says that, when used in combination with building-integrated solar photovoltaic, Ice Bears can help fill the “post solar hole,” balancing energy supply and demand mismatches that occur throughout the day.
For example Tropsa says, on hot days, the building’s demand for air conditioning continues to rise late into the afternoon “because of the gain from the sun throughout the day and shoppers coming into the stores” after work. Meanwhile, he says, power output from the building’s solar arrays begin to decline in the afternoon, as the sun sets on the horizon. The Ice Bear can help fill the gap, leveling the building’s electricity demand during the later part of the afternoon by “delivering that makeup energy” stored in the form of ice from the previous night.
Cool Data architecture allows the utility to control how much energy it stores up, by cycling individual Ice Bear units between operational modes, and how much demand it can bring onto the grid.
Tropsa points out that, when packaged with GIS, Ice Energy’s software can also keep the utility informed “exactly where those assets are on the feeders, or within the utility service territory. So if they see a need to take a load off the grid—if they see a five-megawatt cloud bank running across the southern part of their territory, they can switch Ice Bears on or off,” to offset the variability in output from grid connected solar panels.
“Storage is a load managing tool that the utility is using every day all the time; so it’s very useful,” continues Tropsa. “What’s great about storage is, it’s bidirectional. Now if we want to talk about ice, plus sun, plus wind, the ice solves the problem for the utility between noon and six, and then at night, when they’re looking for a place for the wind power, we store that wind energy. So we create a very useful element of the emerging renewable energy resource grid.”
Good for Business
Tropsa believes the market potential for storage could be as high as 100 gigawatts. “It’s going to take decades for energy storage to continue to grow in the marketplace,” he says.
For that reason, he believes technologies, such as Ice Bear installations, can also translate into numerous jobs in the HVAC trade.
“While the contracts will be installed over one or two years, they are going to be followed up with other contracts in the same areas as we continue to grow, as the economy comes back, and the demand for energy grows.”
Writer David C. Richardson is a frequent contributor to Forester publications.