Featured The Dirty Truth About Combustion Engine Vehicles

Home solar and commercial PV farms aren't directly comparable. The home owner is putting in solar to cover their own use; not to sell production. The farm could use its buying size to get better prices for panels, which could mean more efficient and higher output ones, but they also have to buy land to set up their panels on. For an electricity producer, a central plant or farm is more cost effective. Spreading that field of panels out over multiple buildings means increasing the cost for connection to the grid, as each location will need its own set of equipment for that. Plus less is spent on inspections and maintenance if all the panels are at one location.

As for the tiles, all roofs need a roofing material. Tiles doing double duty is only an issue if they cost substantially more than roofing of equivalent lifespan and separate PV panels.

edit: Regarding off grid and Hawaii. Much of the terrain is pretty mountainous, with occasional lava flows. Running utility lines everywhere isn't cheap. I suspect much of the off grid installations are places that simply wouldn't have electricity otherwise.

 

Hydrogen is not a good choice for storing grid energy and returning it to the grid. Batteries and curtailment are better. Hydrogen is only a good way to store grid energy if you are going to use it later in transportation applications.

 

This is not at all what the NREL says.
NREL study backs hydrogen for long-duration storage – pv magazine USA.

Batteries are very good for grid stability, when minutes or hours of power are needed. They are not good for storing days worth of electricity. Here despite the inefficiencies costs for an island like hawaii may be much lower. It is a really bad method for light duty transportation in hawaii as it is likely that bidirectional bevs like the ioniq 5 and smart chargers can help buffer daily renewables. Hydrogen may be appropriate for heavy duty vehicles, but not for long haul trucking.

 

Yeah, I don't buy it (and I work at NREL, and have also published studies on this). The reason is, the cost of the storage is around 3x the cost of the energy, even if the storage cost is nothing. That's because the round-trip efficiency is around 1/3.

Right. So you need hydrogen for season storage, you just don't return that energy to the grid.

Long-haul trucking is on-highway so BEV is a better choice. Off-highway uses (construction, mining, etc.) and mobile uses (cars, ships, airplanes, etc.) are a far better use of hydrogen than returning it to the grid at 35% round-trip efficiency.

 

Could you elaborate this point? Are you also suggesting there is no room for improvement on this front?

 

HHV for Hydrogen is around 39.4kWh/kg (from memory). If your electrolyzer is 100% efficient, that's what you'll need to put in to get hydrogen out. When you run it through a fuel cell, you can get at most the LHV of hydrogen which is 33.3kWh/kg. So that's 85% efficiency if both of your devices are 100% efficient. Obviously, that's not possible in practice. In practice, your electrolyzer may top out at 80% efficient or so and your fuel cell around 60%. 85%*80%*60% = 41%. So that's about as good as you can do. In reality, we don't do that good, hence 35%.

Essentially the problem is, you lose the HHV-LHV energy and the efficiency loss of two separate devices. When you multiply all that together, you get a lot of loss, especially since Hydrogen has (I think) the largest difference between HHV and LHV of any substance.

Batteries are closer to 85% and can be better than that. That's why you don't want to return the energy to the grid, except in very rare cases. Transportation energy is far more valuable than grid energy so you want to use your expensive energy there.

The reason you don't want to use batteries for seasonal storage is that they aren't very good energy storage devices. They're efficient but they are heavy and extremely expensive. So you want to use them only when they are needed - short distance transportation and fast-response on-grid. In reality, these large on-grid batteries shouldn't be needed. We should be using V2G for that instead (using the batteries in EVs as the storage source). If you have enough EVs, you might even be able to get away without V2G and just use the chargers as a dispatchable load. But it's still only daily, not seasonal. Seasonal is HUGE.

 

And when solar production is reduced during the rainy season, what supplies the shortfall to the grid?

 

well 40% in what I showed you, 33% in your opinion, not that it matters much. What is the cost of the energy in hawaii if it is tanked in oil versus solar + storage? Hydrogen makes no sense in texas, but does in hawaii. Have you looked at the context? If you can get solar/wind/wave/geothermal for $0.10/kwh and store excess and put it back on at $0.50/kwh and you are going to do well compared to alternatives. You have to overbuild less. If hawaii can stop importing $5B/year worth of oil it makes sense.

Why not in hawaii's case? Or in remote locations?

I haven't seen a decent business case for converting mining or construction to hydrogen. Proterra is working with Komatsu on bev excavators. With battery prices falling this will start to make sense in a decade. I see anglo american is doing an experiment with hydrogen fuel cell trucks in a south african open pit mine. We will see if it works, but like most ventures like this IMHO it will fail.

 

Over-building of the source.

The idea is you build the source for the worst time of year and the rest of the time you use the excess to make hydrogen for the uses I mentioned, storing it. You can actually return a small amount to the grid in the worst case but you want to minimize that. My optimization routine always optimized that to zero. I did a model using a year of 10 minute data.

 

Hawaii is unique (and not monolithic - the islands are all unique). It may make a tiny bit of sense there but Hawaii's issue is that they don't have a lot of underground storage locations either. So there it probably makes the most sense to over-build and curtail.

 

There are a ton of construction activities at locations that don't have a grid. For example, building a collection system for a wind farm. There is no grid yet (you're building it) so where are you going to charge? The same goes for things like clearing and dredging. If you're out in a swamp in the woods, what are you going to do to charge when the nearest grid is a load-and-tow away?

In cases where there's a grid, BEVs are just better. But that's not always the case at all, and that's why the vast majority of construction equipment runs on diesel. A few things run on direct grid energy (literally drag an extension cord). I have some of this "cord" in my office (3-phase 4-0 4000V mining cable). It's cool stuff! But only if you have the grid.

 

My discussion of this was not lots of islands, it is oahu. You seem to be poo pooing it without reading and thinking. Oahu wants to go 100% renewable for its grid by 2045. I am not going to judge the timeline or the 100% (90% seems a lot easier), but how much would you need to overbuild to achieve this versus say building some storage?

 

So have a MSR baseload nuclear plant + a peaker + wind/solar so you have a large enough installed base of power

 

I was at a wind farm on Oahu (North shore). I was on top of the Mod 5 turbine there and two of the turbines I work on at work came from there. I'm somewhat familiar with the island.

Generally, you're looking at 2x over-building vs 3x energy loss, or thereabouts. And don't forget, you can (if you work at it) use the excess energy from the overbuilding instead of wasting it in energy loss.

 

I doubt many people will tolerate the idea of having to handle high-level or low-level nuclear waste from a new nuclear powerplant, especially on an island.

 

Ok then you can probably calculate the answer.
2x over build means you are throwing away half the energy. In texas that would also mean black outs on hot summer and cold winter days. There is a lot of seasonality.


Now I'm cheating here, and looking at someone else's work for hawaii. What if you had 36% battery storage and and 4% long term storage? Now you only need to over build 50%. That battery storage is expensive but it keeps the total system price down. Say the long term storage is hydrogen and it takes 12% of your electricity to get 4% back out. From the a system level isn't that better. Its hard to know prices when hawaii gets further along, but there is likely a need for long term storage. There is definitely a good trade off with long term storage at some point.

 

No, it doesn't.

It doesn't mean that either.

Then you've got nowhere near enough long-term storage. Well, maybe in Hawaii where the temperature never changes...

But 4% and 36% of what?

Long term storage is mostly-free when you have gas underground. Long term storage in Hawaii using hydrogen returned to the grid will be outrageously expensive.

 

If texas went 100% renewable and we only built to 200% of peak, there would of course be black outs. I don't know what 200% in your example means.

The electricity used.

I see some hand waving but 0 thought in this answer. During the black outs electricity spot prices in texas went to $12/kwh. In summer they ogo above $1/kwh for short periods of time. How much is outrageously expensive? Retail price of electricity in hawaii right now is about $0.35. How much would hydrogen storage cost per kwh? Outrageous seems seems like a bad answer. Is it $2/kwh. That seems reasonable for seasonal storage. I think its lower than that. Remember it will be a small percentage of total energy use.

But you said you work for NREL. Yell at them to stop experimenting.

 

The same as you said here:

That's because Texas' electricity market is as dumb as a sack of hammers.

6x average

Multiply by 6 or so.

On the mainland, it's currently under $0.01 (plus the energy).

Maybe in Hawaii but on the mainland, it's actually quite huge. I have previously used the example that it's over a century and a half of gigafactory total output - each year.

Just have to be smart.

 

Wind?

along with PV & massive battery backups - they are already working - many islands such as Kauai.

Tesla is powering the Hawaiian island of Kauai with more than 54,000 solar panels and its giant battery packs | The Independent | The Independent

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