The debate goes on between fuel-cell vehicle (FCV) advocates and those who think electric vehicles will win the day. Toyota’s R&D chief disses electric vehicles because of poor range and long charging times, even as BMW’s new i3 pure electric is selling quite well and wows consumers.

We now have an apparent divide between major automakers, with Toyota, Honda and Hyundai pushing hard for FCVs as the future, and GM, Nissan, Tesla and BMW now offering impressive BEVs (pure electrics or plug-in hybrids) that clearly aren’t just compliance cars for the California market, as is the case for the new round of FCV offerings.

BMW also just began offering a very affordable and compact DC fast charger to BMW dealers; at $6,500, it's far cheaper than has historically been the case for fast chargers. This fast charger can bring the i3 to an 80 percent charge in 30 minutes, at no cost to the car owner through at least 2015.

Studies have found that FCVs are far less efficient at using electricity as a fuel than are battery electric vehicles (BEVs) or plug-in hybrid electric vehicles (PHEVs). For example, a recent UC Irvine analysis found that using electricity in BEVs directly is 2.5 times more efficient than using that same electricity to create hydrogen for use in FCVs (see the chart on page 2 of the link). The only other study I’ve found looking directly at this issue is a 2001 study that mirrors the UCI investigation’s conclusions, finding that about 80 percent of the energy is lost from converting electricity into hydrogen and then back into electricity in a fuel cell.

My last piece focused on this issue, identifying it as a major stumbling block for public policies that support FCVs. This follow-up article will examine a related argument that some FCV advocates have made. Essentially, the argument states that even if FCVs are less efficient at using renewable electricity than BEVs, the grid reliability issues associated with a higher penetration of BEVs and renewables will still justify use of FCVs. These advocates argue that using renewable electricity to create hydrogen will avoid curtailment and will mitigate overgeneration issues associated with, for example, the increasing availability of peaking solar power in California and other jurisdictions as solar power growth continues its meteoric rise. The hydrogen created from excess solar power, the argument goes, can then be used in FCVs as a fuel, while also providing grid support.

Here’s a simplified summary of my conclusions for those who don’t want to delve into the details of this kind of technical discussion: the "grid benefits" arguments in favor of FCVs don’t seem to hold much water. The more plausible view is that BEVs are actually better for the grid in terms of improved reliability, as well as increased efficiency and less cost.

Let’s look at each of the main claims of this pro-FCV argument.

Claim 1: Using excess renewable electricity to electrolyze hydrogen is independent of travel demand and BEV battery capacity.

It is technically true that using excess renewable electricity to create hydrogen is, when considered alongside the alternative BEV approach, independent of vehicle travel demand and the available BEV battery capacity. However, this fact isn’t particularly relevant if state-level projections for BEV sales are accurate.

The California Energy Commission projects that up to 33,000 megawatts of EV (plug-ins and pure electrics) storage will be available to the grid by 2022 (see Figure 1). This won’t translate, of course, into usable grid storage at the same capacity. However, even if 10 percent of this projected capacity is made available to the grid through smart charging or “vehicle-to-grid” programs, this will be a major contributor to grid stability. Moreover, this aspect of BEV availability is a beneficial side effect of BEV sales more generally.

The California Public Utilities Commission is currently considering how best to incentivize smart charging, which the CPUC defines as the ability to turn the charging of BEVs on or off as the grid requires. With smart charging, there is no flow of power from the vehicle to the grid (known as V2G), but the end result is much the same as that from smart charging. This is the case because turning off a BEV that is currently charging has the same impact as a BEV sending power to the grid, but with the impact divided by two, because the battery cannot be discharged back to the grid. In other words, stopping power that is flowing into a BEV has much the same effect, but to a lesser degree, as sending power back into the grid.

FIGURE 1: California Energy Commission Projection for Grid Load From EVs and PHEVs

Source: CEC California Energy Demand 2012-2022 Final Forecast

The California Independent System Operator projects that very little storage will be required to balance variable renewables by 2020, which is the deadline for utilities to achieve the 33 percent renewable standard. The CPUC has also mandated that 1.3 gigawatts of stationary storage must be procured by the investor-owned utilities and brought on-line by 2024.

It's important to acknowledge that the degree to which BEVs will be able to provide grid stability will depend not only on how many owners can be induced to opt for smart charging, but also on how often and during what times of the day BEVs are connected to the grid. So while BEVs that are signed up for smart charging (or, better yet, V2G) will clearly provide grid reliability benefits, there may well still be overgeneration at times, even under optimistic BEV adoption rate scenarios. If that is the case, there may be a role for some other types of storage as alternatives to curtailment, which is probably the least attractive alternative for a variety of reasons.

A recent report from E3, a California-based energy consultancy that provides regular guidance to the CPUC, found that stationary long-term battery storage options, in a 40 percent renewables scenario, can save up to $300 million per year as an alternative to curtailment. If these calculations are at all accurate, investor-owned utilities will very likely benefit from substantial on-peak charging of BEVs, and also from on-peak charging of stationary storage facilities.

The relevant question now under discussion is whether adding the infrastructure necessary to use hydrogen as an additional electricity storage medium is justified by the economic benefits of hydrogen storage, including consideration of the large conversion losses from doing so.

In sum, through the 2020-2025 timeframe, it seems that a combination of limited requirements for storage on the grid by 2020, existing goals for energy storage beyond 2020, and the expected pace of BEV availability on the grid, will likely render moot any benefits derived from hydrogen creation from excess renewable electricity -- particularly when we remind ourselves that such use is 2.5 times less efficient than using that power directly in BEVs.

What about beyond 2025? Well, BEV sales are likely to increase even faster at that point, as new models come on the market and costs and technology improve. And as BEV owners learn more about the benefits of smart charging, it is likely that we’ll see higher levels of participation, providing further grid support as an incidental benefit of BEV sales.

Claim 2: BEVs will require more renewable electricity on the grid, and that will require more backup power to balance out the variable renewables like solar and wind.

This argument seems to ignore the fact that California already has laws requiring that utilities achieve 33 percent renewable energy by 2020. There is also a growing push to create a new law requiring up to 51 percent renewables by 2030. So any grid reliability issues that stem from higher penetration of renewables are independent of policies that support BEVs. And as just discussed in detail above, BEVs actually provide major grid reliability benefits. In fact, the quantified grid benefits from a number of studies suggest that BEV owners could be compensated as much as $100 per month due to the grid reliability benefits from smart charging of their BEVs. This has prompted some intervenors in the CPUC proceeding examining these policies (R.13-11-007) to suggest that BEV owners could be provided free power for all driving in return for allowing smart charging of their vehicle. The CPUC has not yet issued a decision on this matter.

Claim 3: Use of FCVs provides more inherent storage capacity than BEVs.

This argument also hinges on the ability to create as much hydrogen from grid electricity as one wants to, with storage being fairly easy compared to the battery storage alternative. However, again, it will require a large new infrastructure to create the hydrogen at issue, and the conversion losses of turning electricity into hydrogen and then back into electricity in fuel cells entails a loss of 70 percent to 80 percent of the energy. If we can, instead, use BEVs as already-existing energy storage facilities that can utilize this excess electricity at 2.5 times the efficiency of hydrogen production, why wouldn’t we pursue the BEV route?

Claim 4: Using excess electricity to create hydrogen allows for more efficient gas generator operations.

Gas generators are still needed for the evening ramp as demand peaks from people returning home after work, while solar power production diminishes to zero. This is the “neck” of the famous “duck chart” (Figure 2), which projects the load curve out to 2020 as more and more solar and wind comes on-line. The duck chart suggests that there will also be an issue with overgeneration during midday periods because fossil generation is unable to turn down below a certain level. This is the “belly” of the duck. FCV advocates have argued that these two issues can better be addressed through H2 production from excess power than with BEVs.


FIGURE 2: The Duck Chart

Source: CAISO

In terms of the belly of the duck, BEVs are a well-fitted solution to flatten the belly if incentives for daytime charging are provided, as discussed above. The Clean Coalition’s “Flattening the Duck” presentation is available online and shows various ways, including using EVs to mitigate overgeneration, to reduce issues illustrated by the duck chart. The belly is already becoming real today (see Figure 3) as solar production grows quickly in California, mostly at the utility-scale level. Figure 3 shows CAISO’s grid from July 26, 2014, with about 4,000 megawatts of wholesale solar production on-line at times, during a peak grid-wide demand of almost 40,000 megawatts.

Another benefit: as the belly problem is solved, the neck problem becomes less severe as well, because the ramp is reduced in direct proportion to how much the belly is reduced. As such, solving the overgeneration issue would be a “two for the price of one” fix.

FIGURE 3: Recent Renewables Production Levels in California

Source: CAISO

Workplace charging for BEVs is expanding, and with the development of low-cost Level 2 and 3 chargers (like BMW’s fast charger), it is reasonable to believe that we are well on our way to a robust daytime BEV charging infrastructure being built out. California already has almost 2,000 EV charging stations with more than 5,000 outlets. Growth has been very rapid, with the large majority of these stations being built in the last five years. 

If substantial incentives are provided to BEV owners for daytime charging, due to the grid benefits of doing so, it is reasonable to believe that we’ll see a steadily growing contribution from BEVs to reducing the belly of the duck. We’re already seeing firms get serious about coordinating these kinds of solutions; for example, EPRI’s Open EV Tech platform was recently announced. This new aggregation platform brings together eight different automakers under a single standard.

I agree that the neck of the duck is a problem that will require significant firm capacity to remain on-line until sufficient stationary or mobile storage is available. However, V2G (two-way charging) could mitigate this problem significantly in much the same manner as V1G can mitigate the belly problem. Moreover, because V1G provides the same (but at half the capacity) benefits of V2G, even if V2G doesn’t become reality in the next decade, we’ll still see a substantial contribution to the neck problem from BEVs as smart charging allows plugged-in BEVs to be stopped from charging during the neck.

Similarly, the 1.3 gigawatts of energy storage mandated by the CPUC, which includes mobile and stationary storage, will further help with the neck problem because all of this storage will, at least in theory, be available to produce power during the neck period.

Finally, and perhaps most importantly, it would probably make more sense to simply use natural gas in fuel cells directly (as with the Bloom Box stationary fuel cell), for grid stability purposes, rather than using natural gas to create electricity in a power plant, convert that excess power remotely to hydrogen and then convert the hydrogen back into electricity in a fuel cell to supply power back to the grid during ramp times. The efficiency losses of the latter pathway are staggering, not to mention the additional infrastructure required for hydrogen production, storage and energy production.

Clearly, my thoughts here are preliminary and sketchy. New data will require reassessing my conclusions. The same UC Irvine team that released the report I cited here is currently modeling the grid benefits of FCVs and BEVs. Their work is also preliminary at this point, but we should have complete results in the coming months. I’ll check back in on this issue once the results are made public.

A major new report from the Edison Electric Institute urges the U.S. utility industry to get serious about buying BEVs for their fleets, as the “point of the spear” for electrification of transportation. The report states: “Electrification of the transportation sector is a potential ‘quadruple win’ for electric utilities and society, and will enable companies to support environmental goals, build customer satisfaction, reduce operating costs and assure the future value of existing assets.” The report also highlights the fact that battery costs have come down 50% in the last four years.

This and many other similar reports are very encouraging regarding the degree to which BEVs are already being taken very seriously.

In sum, looking at the broader grid reliability issues associated with FCVs and BEVs doesn’t seem to offer much, if any, advantage for FCVs.


Tam Hunt is owner of Community Renewable Solutions LLC, a renewable energy project development and policy advocacy firm based in Santa Barbara, California and Hilo, Hawaii.