Six home battery among strategies to contour demand around intermittent resources
by Allen Best
On the cusp of deep penetration of renewable energy that most would have thought impossible just a decade ago, Holy Cross Energy has now started working to contour demands around those intermittent renewables.
Consider the six Tesla Powerwall battery packs installed in recent months in the homes of Holy Cross Energy members. They look vaguely like sleek, slender, and small refrigerators. They serve a similar purpose, storing a perishable, renewable energy, to be tapped when demand peaks.
Peak demand in the Holy Cross service area between Vail, Aspen, and Parachute typically occurs during winter evenings. If tests in coming months bear out expectations, Holy Cross hopes to have 100 more batteries installed among its 55,000 metered members by the end of 2021.
Power+, as the pilot project is called, is among several programs launched by Holy Cross Energy to juggle demand to better match supplies of renewables.
This transition to clean energy has been accelerating. In 2019, renewables were responsible for 44% of electrical generation consumed by Holy Cross members. By the end of 2022, renewables may have delivered more than 70% of electricity for the year.
The biggest single stride will come from a wind farm near Arriba, located about 120 miles east of Denver along Interstate 70. This wind farm will deliver 100 megawatts for Holy Cross, enough to supply a third of total demand. It’s slated for completion by New Year’s Eve 2021. Hunter Solar, a solar installation near Bennett, 35 miles southeast of Denver, will deliver another 30 megawatts by July 2022.
Construction of a 5-megawatt solar farm near the Aspen/Pitkin County Airport is expected to begin when the snow melts next spring, with service beginning next summer.
The three projects together will get Holy Cross to 70% renewables of annual energy production in 2022.
Next comes the work to reach 80%. Holy Cross expects to hit that level by the end of 2024—and perhaps even 85%.
And this just in: a press conference on Monday, Dec. 14, for “a special announcement regarding the next chapter in HCE’s commitment to a clean energy future.”
In early 2020, Holy Cross invited proposals for new electrical generation. This time, it said, it favored local sources. Too, the projects needed to lower costs, with the savings to be transferred to Holy Cross customers.
That invitation yielded 51 proposals. Among the first chosen was a 4.5-megawatt solar array to be constructed near the Colorado Mountain College Spring Valley Campus, between Glenwood Springs and Carbondale. Several other projects chosen have not been announced pending final scrutiny of contract details.
In deciding which projects to pursue, Steve Beuning, the vice president for power supply and programs at Holy Cross, describes several considerations:
First, does the new generating source create a situation of over-supply? “Over-supply is when the sun is shining and the wind is blowing and our members aren’t using much energy,” explains Beuning.
An office building sitting empty is costing somebody lots of money. Ditto for a rarely used wind farm or solar array. Construction is not cheap, even if the wind and sunshine are free. Best is when demand can take full advantage of all renewable resource production.
Second, does the proposed solar farm or other resource clash with the utility’s existing contract with Public Service Co. of Colorado, a subsidiary of Xcel Energy? Xcel is a major provider of electricity for Holy Cross. The contract, which was initiated in the early 1990s, specifies the circumstances under which Holy Cross can substitute supplies against those contractually committed to Holy Cross by Xcel.
“What we don’t want to do is buy energy twice,” says Beuning.
Third, what Impacts will occur to the delivery system of Holy Cross? Will the electrical wires already strung accommodate the new energy? A related but more abstract consideration has to do with reliability. How does this new generation affect grid stability? For example, will the loss of generation cause the lights to flicker or, worse yet, cause your computer to crash—causing you to lose that document you had slaved on for an hour but forgot to save!
One solution to this need to maintain steady deliveries may be through development of autonomous, local, so-called micro-grids. The Power+ program from Holy Cross is an example of a micro-grid that helps a single retail customer. In the future the concepts behind this program could be expanded to cover multiple customers with backup supply.
Power+ is one among several programs that seeks to buffer these rough edges between demand by consumers and new renewable energy supplies. Take Power+, the program that will put Tesla batteries into homes. During times of oversupply, they provide storage for consumption later, when renewable production is less but demand may be more.
Holy Cross offers incentives for those participating, but other members benefit, too, as the storage allows members, not just those houses with batteries, to take full advantage of lower-cost renewable energy.
Peak Time Payback, another voluntary program, also works at the fulcrum of supply and demand. Those members participating agree to get messages that request deferring electrical demand. Participants could then choose to delay using their washers and dryers during the evening, Presidents’ Weekend or some other time when Vail and Aspen are bustling and everybody is getting ready to watch the latest Netflix offering. The same thing can be achieved during a time of hot weather by moving the thermostat of an air conditioner up a few degrees, to reduce electricity use.
The intent of this program is to shave peak demand, typically during two or three hours blocks. This averts the need for Holy Cross to buy electric capacity on the open market at its most expensive moments. Participating Holy Cross members can, to the extent they alter their demands, benefit from preferred rates.
GreenUp, another pilot program, provides the flip-side to Peak Time Paybacks. It is premised on the fact that there are blocks of time when wind and solar forecasters predict an abundance of renewable energy. Again, there are financial incentives, but this time inverse to those intended to shave peak demand. In this case, consumers are encouraged through lower costs to actually use electricity when its plentiful.
“We will make the decisions to trigger the program based on our forecast for wind and solar, and the member would make the decisions about any behavior changes to access the reduced rates,” says Beuning. “We will communicate the program timing through a text or e-mail.”
Other utilities offer similar demand-side management programs in an effort to contour supplies with demands more efficiently. It made sense even when most electricity was generated by burning fossil fuels. Deepening penetration of intermittent renewables will require even greater juggling of demand.
The arrival of electric cars and other vehicles will pose both additional challenges but also offer opportunities for optimizing the balance between supplies and demands.
Holy Cross in recent years has gained a national reputation for innovation and boldness. Platte River Power Authority, which serves four member cities along the northern Front Range, has also started to turn heads.
In 2018, both Colorado utilities adopted ambitious goals for 2030. Holy Cross was first, with its target of 70% renewables and 70% reduction in greenhouse gas emissions in its generating portfolio by 2030. Just a few months later, Platte River Power Authority adopted a resolution calling for 100% carbon-free electricity by 2030.
Now, the two utilities face many of the same challenges, as do other utilities. Platte River’s directors noted that 10 conditions would have to be addressed to achieve its 2030 target. Among those conditions is the need for matured battery storage technology along with steep cost declines.
Another is for a regional transmission organization, or RTO. An RTO enables more efficient access to the electric grid and pairs demands with renewables across a broader geographic area. The idea of improved dispatch and transmission is to allow Colorado and California to work more in tandem, along with Utah and Arizona and other states. An alternate idea would have Colorado sharing energy and demands with states in the Great Plains and their bounteous supplies of wind.
Integration of geographically diverse markets will give Holy Cross greater flexibility, says Beuning, allowing it to deepen the penetration of renewable energy. Think of using California sun to heat water in the late afternoon, or Colorado wind helping address the evening reduction in solar generation in the desert Southwest.
Twenty-five years ago, changes were few from year to year. Now, they’re happening at an almost blinding pace.
The race is on toward 100% carbon-free electricity, but there’s a lot of hard work ahead.