The U.S. power grid, built over the past century, is under increasing threat from extreme weather events, rising costs, and the urgent need to reduce greenhouse gas (GHG) emissions. The energy industry has both the mandate and the opportunity over the upcoming decade to transform the grid to deliver affordable, reliable, net zero-carbon electricity. We will achieve this through the rapid development and deployment of innovative new electricity generation, storage, and transmission technologies.

Solving the Intermittency Gap

The most promising path to a net zero-carbon electricity system is to increase renewable power, particularly solar and wind, by orders of magnitude while rapidly reducing reliance on fossil fuels. While we know this is the correct path, the problem is that renewables are naturally intermittent – the sun isn’t always shining and the wind isn’t always blowing. They vary widely from hour to hour and across weeks, months and seasons. Many consecutive days can pass without substantial sun or wind near major global cities, and solar resource potential can be less than half in the winter than it is in the summer.

Renewables are Highly Intermittent
Large Gaps, Steep Ramps Across Hours, Weeks, and Seasons

Renewables are Highly Intermittent
Large Gaps, Steep Ramps Across Hours, Weeks, and Seasons

       CAISO Summer Day

       CAISO Winter Day

Source: CAISO.  Summer data from 6/16/20 and winter from 12/23/19.  Solar and wind resources are shown at two times the data.

Baseload power sources, such as zero-carbon nuclear power or low-carbon fuel cells, can keep a steady minimum of power available at all times, but they are missing a capability essential to the grid of the future: they cannot quickly dispatch power to ramp up or down to follow changes in power demand or in solar or wind electricity generation. 

In order to make the broad use of renewables reliable and efficient, we need to pair them with dispatchable power generation or storage systems that can ramp up and down or turn on and off as fast and often as needed. 

Additionally, these dispatchable resources must also be distributed, or deployable near their renewable counterparts or load centers. In California, the state with the highest amount of renewable power, about 65% of renewables curtailment today is caused by local congestion constraints.1 Distributed generation mitigates locally-driven curtailment as well as the lack of national long-haul transmission lines. It also helps circumvent constraints in both rural and dense urban areas as electricity demand rises, and enables microgrid deployment to support smart cities, commercial or university campuses, electric vehicle charging stations, and a variety of other critical infrastructure. Lastly, it provides robustness from grid outages caused by extreme weather events.

Thinking Beyond Batteries

The conventional thinking among many today is that batteries alone will answer these challenges. Without a doubt, batteries will continue to play an increasingly important role by supplying electricity during short-term intermittencies or shifting some of the peak solar energy from the afternoon into evening to better fit demand. However, until significant advancements are made, batteries will not be economically feasible for addressing prolonged, multi-day outages or seasonal variation in renewable energy generation. 

In a 2018 study, researchers at Caltech estimated that a US electric grid consisting of only solar, wind, and energy storage, with reliability consistent with today’s grid (99.7%), would require three weeks of storage (227 TWh). Even at a reduced average storage cost of $100/MWh, this would cost $23 trillion – equivalent to 62 years of total annual U.S. electricity expenditures.2,3 The authors note that the $23 trillion figure also assumes “perfect” transmission of electricity across the U.S. grid, making these cost estimates highly conservative. While we should continue to invest in research for batteries, it’s clear that we need innovation across a portfolio of energy technologies.

   We need
dispatchable,
low cost,
    fuel-flexible generation

to firm intermittent
renewables.     

In a 2018 study, researchers at Caltech estimated that a US electric grid consisting of only solar, wind, and energy storage, with reliability consistent with today’s grid (99.7%), would require three weeks of storage (227 TWh). Even at a reduced average storage cost of $100/MWh, this would cost $23 trillion – equivalent to 62 years of total annual U.S. electricity expenditures.2,3 The authors note that the $23 trillion figure also assumes “perfect” transmission of electricity across the U.S. grid, making these cost estimates highly conservative. While we should continue to invest in research for batteries, it’s clear that we need innovation across a portfolio of energy technologies.

 

We need dispatchable, low cost, fuel-flexible generation to firm intermittent renewables.

Former U.S. Secretary of Energy Ernest Moniz, speaking in a June 2020 talk at Stanford University, underscored the need for broad innovation and rapid deployment across numerous generation and storage technologies: “We see lots of statements about electricity decarbonization by 2030 based upon wind, solar and batteries. This is what I term ‘Magical Thinking.’ It cannot happen in that way and in that timescale…We need a decade of all-out innovation and deployment.”4

The Value of Dispatchable and Distributed, Fuel-Flexible Generation

We must be looking at other options for long-term, clean dispatchable and distributed resources that can firm renewables. One highly promising area is to store energy in renewable fuels to cover weekly and seasonal intermittencies. In much of the U.S. today, the gas grid enables low-cost, reliable, dispatchable power, producing nearly 40% of electricity generated. As we transition from natural gas to renewable fuels such as biogas, renewable natural gas, and green hydrogen, we can deliver crucial emissions reductions while enabling a resilient grid with more solar and wind penetration.

This transition has begun and is gaining momentum. There already is enough potential biogas to power 20% of U.S. electricity needs.5 Energy industry leaders and policymakers are accelerating their R&D and commitments for green hydrogen explorations. The U.S. Energy Department in July 2020 announced $64 million worth of funding for hydrogen projects and plans to invest up to $100 million over five years for two new research efforts on hydrogen. The following month NextEra Energy, the largest U.S. renewables generator, announced its plans to build a $65 million green hydrogen pilot plant in Florida by 2023.

We need dispatchable, low cost, fuel-flexible generation to firm intermittent renewables. The path forward is threefold:

  • improve the efficiency of existing gas usage where it can quickly make an impact to carbon emissions
  • add dispatchable, distributed generation capabilities to enable increased renewable energy without curtailment while increasing resiliency
  • accelerate the adoption of renewable fuels to meet gaseous fuel needs within two decades

At Mainspring, We Are Working on All Three

We designed and are commercializing the industry’s first linear generator to maximize efficiency, resilience, and flexibility in electricity production while significantly lowering both emissions and cost. Our linear generators are fully dispatchable, able to track both electricity demands and renewables production. Our products can also seamlessly switch between renewable fuels such as biogas and hydrogen and conventional fuels such as natural gas and propane. Every unit installed builds out the national infrastructure for renewable fuels.

Flexibility to Enable a Net-Zero Carbon Future
Renewable, Dispatchable, Resilient Capacity to Firm Solar and Wind

Biogas

Renewable Gas

Green Hydrogen

Mainspring Generator

Commercial & Industrial Buildings

Grid Distribution

Microgrids

At Mainspring, We Are Working on All Three

We designed and are commercializing the industry’s first linear generator to maximize efficiency, resilience, and flexibility in electricity production while significantly lowering both emissions and cost. Our linear generators are fully dispatchable, able to track both electricity demands and renewables production. Our products can also seamlessly switch between renewable fuels such as biogas and hydrogen and conventional fuels such as natural gas and propane. Every unit installed builds out the national infrastructure for renewable fuels.

Flexibility to Enable a Net-Zero Carbon Future
Renewable, Dispatchable, Resilient Capacity to Firm Solar and Wind

Biogas
Renewable Gas
Green Hydrogen

Mainspring Generator

Commercial & Industrial Buildings
Grid Distribution
Microgrids

Each 250 kilowatt Mainspring product, in the footprint of a parking space, can save 450 metric tons of carbon emissions per year compared to the US average grid running on natural gas, or the rough equivalent of removing 100 passenger cars from the road or installing 375 kW of rooftop solar.6-8 When running on 100% renewable gas it can save 1,400 metric tons, or more than three times as much. At scale, the numbers can be transformative while adding critical resilience and cutting costs for households and businesses alike.

The clean, efficient, affordable, and resilient grid of the future is within reach. By firming intermittent renewables with dispatchable, low-cost, fuel-flexible generation, we can accelerate the transformation of the grid for the benefit of all.

Sources

1. Based on publicly available CAISO data for 2019
2. Shaner et al. “Geophysical constraints on the reliability of solar and wind power in the United States”, Energy & Env. Science, 2018
3. EIA Electricity Sales: More Info
4. Ernest Moniz, Stanford Global Energy Dialogues, June 9, 2020 More Info
5. US Energy Information Administration More Info
6. US EPA AVERT More Info
7.Assumes 25 mpg average fuel economy and 13,500 miles per year
8. Assumes 20% capacity factor solar