From pv magazine USA
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 recent study by two researchers at the U.S. National Renewable Energy Laboratory (NREL).
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 United States.
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 kilowatt, wind power costs of $1,400 to $1,900 per kilowatt, 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.”
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.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.
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% to 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.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: email@example.com.