Oversizing renewable capacity and adding long-term storage are not the only ways to match renewable generation with electricity demand on a seasonal basis, according to a study by two NREL researchers.
Their model showed that reducing average building energy usage by about 60% would be key to achieving the least-cost 100% renewable grid with building electrification. The cost-optimal amount of building energy savings ranged from 52% to 68% across five selected climate zones in the U.S.
For each climate zone, the model also found the cost-optimal levels of renewable capacity, allowing for oversizing, as well as long-term storage capacity and battery capacity. The model also chose an optimal mix of solar and wind generation, based on solar costs of $1,900 to $2,500 per kW, wind power costs of $1,400 to $1,900 per kW, and transmission costs.
Optimal oversizing of renewable capacity to handle year-round energy needs would be 3.2 times annual electricity demand in a climate zone stretching from Kansas to New York, the model showed. Solar in this case would contribute 15% of total renewable capacity with wind contributing 85%. Oversizing renewable capacity is associated with curtailment during mild seasons.
In a climate zone from Texas to Florida, optimal oversizing of solar would be 1.4 times annual demand, with solar providing all renewable capacity.
The study modeled long-term storage as being hydrogen storage in caverns, and using fuel cells to convert the hydrogen back to electricity. It used a capital cost of $161/kWh capacity. Optimal long-term storage capacity in each climate zone, measured in kilowatt-hours, ranged from 1 to 5 times annual average daily kWh consumption.
The authors said that most long-duration storage technologies “are either geologically constrained or still underdeveloped.”
Battery storage was modeled based on a capital cost of $380/kWh. Optimal battery storage capacity in each climate zone, measured in kilowatt-hours, ranged from 0.1 to 0.8 times annual average daily consumption.
Costs of a building’s energy efficiency improvements were based on case study data points found through a literature search. The authors reported those results as being “robust:” if the actual costs were 50% lower or higher, then changes in the optimal amount of energy efficiency would be within 5% of the reported results.
The study also assessed the technical potential of buildings’ load flexibility, such as flexible air conditioning control, and building-sited thermal storage either in ice or in high-temperature ceramic brick. Load flexibility associated with such measures had the technical potential of reducing daily storage requirements by anywhere from 37%–81%.
The authors said that many U.S. states, cities, and municipalities are developing plans to shift to 100% renewable energy.
The study, titled “Optimal strategies for a cost-effective and reliable 100% renewable electric grid,” was conducted by Sammy Houssainy and William Livingood, both with NREL.
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My experience trying to pencil out a solar-plus-storage (plus almost certainly liquid fuel generator) for my huge, definitely not passiv-haus worthy, window-abundant house makes this headline scream the truth.
Well yeah, but today’s reality is that energy decisions are made by entities with a variety of ability and intelligence and information. We have proven that efficiency is the cheapest and most abundant resource. In 2020 though, here in the U.S., for the first time ever, wind plus solar added more clean renewable power to the U.S. electric infrastructure than utility efficiency programs caused to be saved in the same year. Still, efficiency was on top because the other large part of efficiency is the U.S. appliance standards, which this decade are saving about 0.5% per year, added to the 1.2% or so that utility programs are saving.
My point is that efficiency spending hasn’t grown, while wind and solar have. And as much as the most intelligent low cost strategies can be identified, we do a poor job of implementing them that way. I haven’t checked, but I would be very surprised if there was much of any wind and solar development in any of the states in the U.S. which do not have competitive wholesale electric markets supported by state regulation. And certainly, the strong renewables states are closely aligned to the strong efficiency state.
The thing though, is that cheap electricity crosses state lines. Cheaper efficiency does not.
In fact, the U.S. could double total utility efficiency savings per year in a matter of months, simply by raising the efficiency program activity in 44 states to the level of the current best six states. This would cost about $8 billion and save more than $30 billion every year.
And if you want to reduce the need for both storage and renewables at a net negative cost, efficiency is pretty much the only resource.
But why aren’t we taking a look at what prevents the less competitive states from doing these good things?
I know it’s a challenge. But my point is that if we don’t figure that out, then we are more likely to end fossil fuels by replacing them with wind and solar and mechanical or chemical storage than by being smarter.
I figured this out for myself. Efficiency is more complicated. It requires an incentive. Allowing program costs and lost revenues merely creates equity with sales. If you want to save hundreds of millions of dollars or billions of dollars, you have to share some of the savings with the utilities. Not much. But in Ohio the utilities proposed 15% and got 13% and did a magnificent job, until the Republicans corrupted the entire process out of existence. I’m keenly aware that other pro-efficiency advocates disagree with me. But there’s the evidence. What we do about it remains to be seen.
The evidence is that wind and solar plus hydrogen or battery storage is easier for most regulators to understand, and therefore that is what we will get. I don’t have to like it, to recognize that it is the more practical approach. We can go on trying to teach people about the benefits of efficiency after we’ve ended all the death and illness from soot and smog.
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