Renewable Energy Getting Fabulously Inexpensive
Up until yesterday, there has been some level of lingering doubt as to the cost-effectiveness of electricity from renewables in a direct comparison to coal and natural gas. That debate is essentially gone at this point, given Solar Reserve’s bid to produce and sell electricity for $0.063/KWh in Chile, in a deal that will make use of the company’s breakthroughs in concentrated solar PV with thermal storage (which means that the power is “dispatchable,” available 24 hours/day).
Interestingly, all this comes in context with the last gasp of the fossil fuel industry (admittedly a very deep gasp): Trump is elected, the U.S. State Department and the interests of ExxonMobil become one, Trump fast-tracks both the Keystone XL and the Dakota Access Pipelines.
Wow. Interesting time to be alive.
In this case, the proposal allows for either pure solar thermal with thermal storage (mirrors and high pressure steam), or such a system with PV operating alongside. I believe the intention is to not include PV in the project as Solar Reserve has managed to reduce the cost of making steam to such a degree that adding PV would not in this case reduce the cost of 24/7 power.
It does look encouraging. Unfortunately, the article did not address the problem of cloudy weather. Perhaps it is never cloudy in the location that Chile has chosen but the article should have addressed that. If clouds are impossible where the installation is located, it may work out very well. However, there are few places where clouds do not occur occasionally. And, if clouds do occur, far more storage could be required. Whether the additional storage would be practical has not been demonstrated.
Also, the system that Chile is using requires water cooling to achieve maximum efficiency. The information provided does not make it possible to determine whether the system would be practical with the reduced efficiency which would result with air cooling especially if such an installation were located in a desert where air temperatures can be quite high in summer months. Water for cooling is not available in many places where solar power would otherwise be practical.
It has been suggested that instead of using water to keep mirrors clean, compressed air could be used. Perhaps so, but has it been determined that compressed air cleaning would not damage the surface of the mirrors? Has it ever actually been demonstrated?
As one commenter stated, the higher temperatures available with a power tower system would make the Brayton cycle practical and eliminate the need for water cooling. But, as the same commenter also stated, there are currently no thermal storage technologies available to store heat at the higher temperatures required to make the Brayton cycle practical.
We really need more information to evaluate Chile’s system adequately and determine whether it would be possible in less ideal situations. It is entirely to easy to wax excessively enthusiastic when adequate information is not provided.
I believe the area of Chile involved is a high altitude desert with pretty much the highest levels of direct sunshine on the planet.
Re the need for substantial excess storage – I would not regard this as much of an issue as the majority of the load is for mining. This being the case, very occasional requests to turn off heavy plant for a few hours to preserve supplies for essentials should not be much of an issue – especially where the alternative is to haul thousands of loads a year of fuel to remote locations.
There is work going on to use flowing sand to store heat – think hour glass, as well as very high temperature options for molten glass, or molten silicon
Gary,
Perhaps in places where most of the load is refining aluminum having periods of insufficient power would not be serious either. In that respect, it would be like mining in Chile. But in many situations, power outages are a very serious matter.
Here is an abstract about an article that addresses high temperature heat storage:
http://www.sciencedirect.com/science/article/pii/S1364032113004735
One problem is that it, and similar websites, require the right credentials to access the information and most of us lack the required credentials. That makes it difficult for many of us to be adequately informed. The same problem exists when trying to get adequate information on medical matters.
They really have come a long way.
I’m struck by the fact that they claim no natural gas usage, but that cannot be true. Molten salt is notorious for freezing up. It would be irresponsible not to have safeguards where you could turn burners on at every section of fluid transfer and storage just to re-melt the salt if it freezes and occludes the flow, especially since the salt in this case will have a long pipe. I’m assuming they only have one storage vault and one turbine generator shared by two towers, so the salt will have to be pumped across the entire width of the heliostat field in each case to a central storage and generation station in between, then pumped back after some portion of the thermal energy has been removed. Freezing has to be a serious design concern. I’d love to see how they designed to minimize it with that low of a bid price.
🙂
That said, this is real progress… and it’s really cool (er… hot).
In the reference to a previous article (“how CSP works”) SK says that the heat loss on the thermal storage is about 1% per day. At this rate the 1.1 GW thermal storage would be losing 11 MW over the course of a day.
The article references “breakthroughs in solar storage” as part of the reduction in price from previous facilities. Perhaps the “breakthrough” is in insulation and this proposal anticipates less than 1% loss? Alternatively it may be the sheer mass of the storage relative to its surface area that reduces storage losses. Either way, this may explain the elimination of a costly fossil fuel backup system and subsequent reduction in price.
I was also interested to see the comparison between CSP with storage and PV with batteries. The former is described as more robust, with better long term economics and able to replace base load fossil fuel plants. The latter were better at load following. It was only a couple of years ago that all attention was turning away from CSP to the rapid price drops in PV.
Ultimately CSP may be an interesting platform if the efficiency of magneto-hydrodynamics can improve enough to take over the heavy lifting from the turbine and the generator. http://www.renewableenergymagazine.com/solar_thermal_electric/magnetohydrodynamics-a-breakthrough-for-high-efficiency-concentrated
Glenn,
It may be more difficult than that. If the salt were to freeze in the center of a long pipe, I don’t see how burners could solve the problem. It seems to me that they’d have to have an electric heating cable over the full length of the piping. The power for the heating cable would have to come from a generator fueled by fossil fuel. However, that may not be a serious disadvantage.
Salts expand and contract with phase changes. That could possibly cause pipes to burst, but I have not been able to get sufficient information to know whether that would actually be a problem.
Perhaps as impressive was JKS’s bid of $0.024 per kWh for a project in India as reported by solar stock analyst Gordon Johnson in the JASO quarterly analyst meeting.