Development of fuelless powerplants?

Well, as for why it hasn't been done on Earth, is there a real advantage over photovoltaic solar power + enough batteries to deal with night/cloudy conditions?

Thucydides wrote:The basic problem is the length of time it would take to "start up" your system (i.e. fill the accumulator with enough molten whatever to start powering things), the intermittent nature of the system (won't work at night, during cloudy weather etc.),

Maybe I'm misunderstanding something, but don't these two problems kind of opposites? I mean, if it takes ages to heat it up in the first place, it should take ages to cool down too... so nights and cloudy weather shouldn't matter much.

Or what am I missing?

the capital cost of the land needed for the mirrors and all the supporting equipment,

At least on Earth, a lot of the really sunny land is pretty cheap. The US Southwest would be a great place for large-scale solar power since there's lots of very sunny, empty desert right next to the cities.

Thucydides wrote:While I think your idea is interesting, you might consider the reasons why a similar technology has not been commercially developed and deployed on Earth, even though we are far better equipped to do so.

After all, most of the technologies you describe have been well known for many years, if not centuries, and variations of these designs have actually been built in prototype form since the oil crisis of the 1970's.

The basic problem is the length of time it would take to "start up" your system.

Such systems are developed right now (2 projects in California and I think Arizona, 1 big one in Spain, they have 2 smalls in service, 1 in Morocco, probably others). The main reason they were not developed before is simple : using electricity is simpler and the capital costs are big. Heated water systems or even concrete blocks one are also created in Germany (those are only for house heating)

But Charis dont have this luxury and use steam as the energy medium while being near equator. In that configuration, this solution is probably viable at least with molten salts as medium. Molten tin is not I think.

Edit : The main company (Abengoa) constructing those plants is spanish, has 2000MW in service and the calfornia project is called Solana and is located in the Mojave.

The main issue on Earth was that the oil/coal industry had 200+ years of development and refinement before anyone thought to build large-scale solar power plants. That drove the prices down and the efficiency up, and renewable sources had to play catchup in the commercial department. Despite that, commercial applications of such plants have already begun appearing.
After all, oil will eventually run out. Sun in the various deserts won't - and where else are you going to use the Mojave as, anyway?

In Safehold, there is no oil industry yet. Building a large-scale refinery isn't less costly than building a large-scale solar plant if you don't have the industry developed for either yet. Also, there's the whole prohibition of electricity thing.

I have 1 little tidbit that MAY have something to say with this, Safehold sun is a little bit farther away from safehold than earth from its own sun, in the books it has been commented that this makes the temperature a little bit lower, so also the power output of any solar powered plant will be lower than their counterpart could be on earth, so the designs would need to be larger, to try and compensate.

This MAY have something to do with the feasibility of this idea.

For myself to tell you the truth I like the design that tom kratman put on his "Carrera" Series, make a solar plant but instead of the solar collector being a photovoltaic cell, is a greenhouse where the air get super hot, and when that hot air leaves through a chimney it pass through a turbine giving you solar power converted to mechanical power just like hydroelectric power in a dam.

Belial666 wrote:The main issue on Earth was that the oil/coal industry had 200+ years of development and refinement before anyone thought to build large-scale solar power plants.

Yeah. I've come to wonder if we might not be farther along by now if Earth hadn't had large easily accessible oil reserves.

Thucydides wrote:The basic problem is the length of time it would take to "start up" your system (i.e. fill the accumulator with enough molten whatever to start powering things), the intermittent nature of the system (won't work at night, during cloudy weather etc.),

Maybe I'm misunderstanding something, but don't these two problems kind of opposites? I mean, if it takes ages to heat it up in the first place, it should take ages to cool down too... so nights and cloudy weather shouldn't matter much.

Or what am I missing?

the capital cost of the land needed for the mirrors and all the supporting equipment,

At least on Earth, a lot of the really sunny land is pretty cheap. The US Southwest would be a great place for large-scale solar power since there's lots of very sunny, empty desert right next to the cities.

For the first part, heating a large enough quantity of the heat storage medium (metals or salt does not really make a difference) will take a considerable amount of time, since the person drawing on the heat energy needs a "clean" and consistent source of heat. If this is taking a long time (especially if you are replenishing a drawn down reservoir after a long cloudy spell) then the person paying you for that heat energy might have to down tools while the accumulator gets back up to operating temperature. Modern industry, especially war industry needs a consistent supply of energy 24/7. Telling them you can't draw so much power at night, or that you can't supply enough power during the rainy season etc. will not make you very popular, and the people depending on that energy might loose business or even go bankrupt since they are not hooked up to a reliable supply. and believe me, the demand for energy will rise very rapidly especially during wartime, enough to put lots of stress on your accumulators.

As for land. the most basic rule of economics is supply and demand. When demand for desert real estate becomes strong, the costs of that land will rise accordingly. Desert land is cheap right now because very few people want to live or work there (compared to temperate climate zones). Make plans to generate large amounts of energy using large surface solar plants in the desert and suddenly you will be paying through the nose for the land.

Thucydides wrote:For the first part, heating a large enough quantity of the heat storage medium (metals or salt does not really make a difference) will take a considerable amount of time, since the person drawing on the heat energy needs a "clean" and consistent source of heat. If this is taking a long time (especially if you are replenishing a drawn down reservoir after a long cloudy spell) then the person paying you for that heat energy might have to down tools while the accumulator gets back up to operating temperature
....

That is not how salts based accumulators works.
Typically salts are heated around 500°C in the reflectors and used to create supercritical steam. After being used in first stage, salts are still about 200°C and can be used either to create secondary steam or stored.

so what is stored is only the excess to need in regard of what is produced. There is usually a high temp (500°C) small tank to deal with the cloudy situation (at least in the existing configs) but the main storage is secondary and made of several tanks not a huge one, so that a maximum temp (around 250°C) is kept in part of the storage. Another thing that makes apart using salts from using metallic alloys is that even if the former drop so low in temp that they go solid, it is still a salt that at worse will form clumps easily grindable that, with a carefully designed circulation pumps system, can still be fed to the reflectors to be restored in liquid form, only more slowly due to the much higher pseudo viscosity.

AFAIK, the 600MW Spain (Solar tres) installation tanks need only 6 hours at 50% charge in summer to compensate night heat loss and energy drawn. They dint go solid in the night though.

As for land. the most basic rule of economics is supply and demand. When demand for desert real estate becomes strong, the costs of that land will rise accordingly. Desert land is cheap right now because very few people want to live or work there (compared to temperate climate zones). Make plans to generate large amounts of energy using large surface solar plants in the desert and suddenly you will be paying through the nose for the land.

There is a major island, the size of a continent, unconsacred right next door and most of Charis inland itself is too. Real estate is not a problem

Yep, for the problems of stable energy supply, you only have an issue if your average demand is higher than your average supply. If you build enough solar plants to cover the demand there's no issue once the plant starts for the first time.



For the supply and demand of land, you raise taxes for undeveloped land. Demand falls and then the government buys it dirt-cheap and builds the solar plants. Also, it might be government-owned land to begin with.

cralkhi wrote:

Belial666 wrote:The main issue on Earth was that the oil/coal industry had 200+ years of development and refinement before anyone thought to build large-scale solar power plants.

Yeah. I've come to wonder if we might not be farther along by now if Earth hadn't had large easily accessible oil reserves.

The bigger issue was solar plants are immobile and inefficient away from the tropics (i.e. Britain, Europe and the America's) where industrialization started. Solar based Stirling engines remained curiosities because of this. Most of the steam engine development was driven by the shipping industry (the coal miners were quite happy with their low efficiency Newcomen de-watering engines - the fuel was free, the tin mines paid for better Watt engines). When hydraulic and then electric power plants were developed they used the proven marine engines for power.

Coal powered steam was an answer to eliminating dependance on the wind for warships and then time critical freight. It was not uncommon for ships to be becalmed for months on end when crossing the tropics - resulting long delays and frequently, deaths on board.

Large scale thermal solar assumes an efficient distribution network, which without electric power just ain't going to happen. Small workshop steam plants and crude or kerosene oil engines will be (and until the 1930's were on earth) very common in every industrialized nation on Safehold.

BYW hot lead tin alloys are VERY corrosive and will eat most metals rapidly and high strength ceramics are a black enough art now without thinking about making high pressure joints on something more brittle than glass. (Utter nightmare for OHS reasons). Molten salts are better but super duplex stainless had better be on the menu.

AirTech wrote: Molten salts are better but super duplex stainless had better be on the menu.

I would agree for fluoride based salts but nitrate based ones at fairly low temps <400°C don't require stainless I think, even if it is what is normally used.
In any case, if dewar tanks are used, they should be either silver or chrome plated and at least the latter should resist corrosion.

Now, can you do the plating without electricity ? I know there is a purely chemical nickel plating method, but I'm not sure nickel is suitable for a dewar coating and don't know if there is an equivalence in chrome or silver purely chemical plating.

Angel gilding, the silvering method for mirrors is not suitable as it is porous.