Author Topic: Space Solar Power with BFR  (Read 70549 times)

Offline speedevil

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Re: Space Solar Power with BFR
« Reply #40 on: 05/02/2018 10:12 am »
Solar might be useful in the tropics, but will always be a marginal player in northern latitudes, which is why Europe is actually a better example. Europe will need nuclear fission, nuclear fusion, or space solar power.

That rather depends on if interconnect is a thing, and 'europe' varies dramatically.
As a consumer, I am paying $0.18/kWh.
Solar panel prices are at around $0.5/W.

Five years worth of power at this price will buy me 7.5kWp of solar panels.

This provides me 9 months of the year or so with a power surplus.
Combining this with daily thermal storage for heating and 3kWh or so of batteries to cover nighttime loads, and this will cover 80%+ of my incoming power bill, for an investment of around 7 years worth of power bills.

If I was in London, it adds another month to independance (as well as having a very large daily surplus in the summer).

I am not here counting export to the grid at all.

I am not counting costs other than panels or batteries., which balances the above out somewhat.

Solar+battery is at a price where for large installations, over the whole lifetime of the system it is somewhat comparable with the price paid to generators for baseload power. ($70/MW). Extra supply would be needed here 3 months of the year.


Offline Robotbeat

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Re: Space Solar Power with BFR
« Reply #41 on: 05/02/2018 11:12 am »
Northern Europe is just a small portion of the world’s population. The vast majority have good access to solar and could rely entirely on it. Not just “maybe in the tropics.”

I agree space based solar power is currently more realistic than fusion.
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Offline AncientU

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Re: Space Solar Power with BFR
« Reply #42 on: 05/02/2018 01:19 pm »
I'm not an electrical engineer and so am out of my depth when discussing antenna dimensions, but is there any way to use a smaller antenna?  How does antenna diameter relate to electrical power, and to distance, and the size of the receiving rectenna?

The microwave antenna and rectenna are large for safety reasons. Sure they can be smaller, but the environmental impact study will be unkind if the power transmission system cooks birds as soon as the fly into the beam. Also has the nasty potential as a weapon system.
Not quite. You can make the Earth receiver smaller (for a given transmission frequency) only by making the space transmitter bigger. That would then concentrate the microwaves to a higher density. I would suggest a legal maximum size of transmitter and power, which would physically limit the beam intensity. (Probably to 1KW/m2).

That way, the only way a SF writer can conjure up death rays, would be by taking over multiple Solar Power Sats and pointing them all at the White House at the same time. (In which case, the President would need to shelter under some aluminium foil).

That's an awful lot of expense to get surface power equal to what the sun delivers for free.
"If we shared everything [we are working on] people would think we are insane!"
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Offline alexterrell

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Re: Space Solar Power with BFR
« Reply #43 on: 05/02/2018 02:55 pm »

That's an awful lot of expense to get surface power equal to what the sun delivers for free.
It's a lot more than the sun delivers for free.

In northern Europe, about 30 times more electricity than the sun delivers. (Solar capacity factor of 10%, and 3 times the conversion efficiency).

Add to that the fact that the Rectenna is much cheaper than solar panels, and still allows light through which can be used for agriculture.

Then add to that the fact that the sun only delivers the power some of the time, and quite rarely in winter, to the extent that the solar has zero capacity value.

Offline Semmel

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Re: Space Solar Power with BFR
« Reply #44 on: 05/02/2018 07:51 pm »
The question for efficiency and cost effectiveness is one thing. But there are other questions..

Maybe the most serious question with solar power is.. what do you do with all the grilled birds that fly through the beam? Or the aircraft that get zapped? Or if the beam wonders off for some reason and starts a huge forest fire or cooks a small town by mistake? Or.. what would the $political_enemy_of_choice think if you start building giant orbital microwave beam weapons? "They are totally for civilian use only!" you say?

Sorry, that got out of hand fast. What I mean is, there are tons of considerations besides efficiency and cost that are very serious.

Offline speedevil

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Re: Space Solar Power with BFR
« Reply #45 on: 05/02/2018 08:30 pm »
The question for efficiency and cost effectiveness is one thing. But there are other questions..

Maybe the most serious question with solar power is.. what do you do with all the grilled birds that fly through the beam?
Some of these can be mitigated by design choices.
If your space power sat is at GEO, and has its antenna and solar panels the same size, if it is under xGW, for a given frequency, the power onto earth can't exceed 1kW/m^2 or whatever limit you think appropriate.
More involved schemes are possible.

Offline Semmel

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Re: Space Solar Power with BFR
« Reply #46 on: 05/02/2018 08:51 pm »
The question for efficiency and cost effectiveness is one thing. But there are other questions..

Maybe the most serious question with solar power is.. what do you do with all the grilled birds that fly through the beam?
Some of these can be mitigated by design choices.
If your space power sat is at GEO, and has its antenna and solar panels the same size, if it is under xGW, for a given frequency, the power onto earth can't exceed 1kW/m^2 or whatever limit you think appropriate.
More involved schemes are possible.

If you had such a large beam, you would need a large receiver as well. Why would you need a satellite in the first place?

Offline RyanC

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Re: Space Solar Power with BFR
« Reply #47 on: 05/02/2018 08:51 pm »
It's feasible.

But for MILITARY applications.

https://www.serdp-estcp.org/content/download/8524/104509/file/FOB_Report_Public.pdf

Quote
Al‐Asad (Iraq) includes 20,000 people living on 18 square miles, with an internal bus system, 48 1
megawatt (MW) generators, 32 MW of continuous power demand, 1.1m gallons of water/day demand,
1.2m gallons of water/day supply, 9 water wells, Reverse Osmosis Water Purification Unit (ROWPU),
water treatment facilities treating 60 gallons/person/day, 6,771 facilities, and 193 spot generators


...


A 600 soldier FOB requires a convoy of 22 trucks per day to supply the base with fuel or water
and to truck away wastewater and solid waste

...

As of November 2007, 80 convoys were continuously
traveling between Kuwait and Iraq (with 70% transporting fuel or water), exposing a critical vulnerability
to Improvised Explosive Devices (IEDs) as they transported supplies from surrounding nations.

...

FOB Planning Factors:

500 man base camp -- 182 kW
1,500 man " " -- 486 KW
3,000 man " " -- 988 KW
10,000 man " " -- 3,293 KW

...

The USMC Energy Assessment team calculated the contractor delivered fuel to Camp
Leatherneck in Afghanistan at $6.39 per gallon, and $11.70 per gallon to deliver the fuel to the tactical
edge (FOB Dwyer, 50 kilometers from Camp Leatherneck).148  An earlier estimate puts FY 02 standard
DESC fuel price at $1.34 per gallon, a “true cost” of USAF tanker‐delivered fuel at $17.50 per gallon, and
“hundreds of dollars per gallon for Army forces deep in the battlespace.”

With all that cost; it's practically cheap to deploy a 10 MW Solar Power Satellite to beam 9MW into remote forward operating bases -- you can use that excess "free" energy to run "moisture farms", basically, use air conditioningn units in reverse to capture the moisture in the air to make water.

Offline CuddlyRocket

Re: Space Solar Power with BFR
« Reply #48 on: 05/02/2018 09:15 pm »
You can sell power on a constant basis greatly reducing the need to ship a lot of mass of batteries too.

You can plan independently of settlement details. A power sat can sell power to most locations on Mars surface. You just have to bet there will be a market for your power to start designing and building power sats.

If there are unexpected finds and people want to set up new outposts to exploit them, you’re ready to sell them power.

On the surface, PV would require more upkeep because of sand and dust than rectennas. PV is easier to deploy and fully automate in space.

You'll probably have to deal with your potential customers concerns as to reliability. After all, if they lose power they're dead! Surface PV might need more upkeep, but is unlikely to go down all at once and access for repair is easier.

Solar might be useful in the tropics, but will always be a marginal player in northern latitudes, which is why Europe is actually a better example. Europe will need nuclear fission, nuclear fusion, or space solar power.

Days are long at higher latitudes in summer and winters are wet and windy. Solar power might be a smaller resource but it's still large - it all depends on the cost, which is rapidly declining.

Originally I wanted to address Musk's erroneous statements and ask whether BFR could enable Space Solar Power, rather than discuss the merits of Space Solar Power.

Any launch vehicle that lowers the cost of access to space would make space solar power more financially feasible. Whether the BFR sufficiently lowers that cost requires a financial calculation (which includes how much power an investment of similar amount in ground-based solar would produce).

Offline RonM

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Re: Space Solar Power with BFR
« Reply #49 on: 05/02/2018 09:16 pm »
Attached is a NASA study titled "Satellite Power Systems (SPS) Concept Definition Study" done by Rockwell in 1980.

Page 14 states "power output must be decreased to satisfy the 23 mW/cm2 (0.23 kW/m2) RF energy constraint in the atmosphere to avoid potential microwave interference with the D and F layers of the atmosphere." Seems to be an issue with microwave power transmission through the ionosphere.

Offline Robotbeat

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Re: Space Solar Power with BFR
« Reply #50 on: 05/03/2018 12:26 am »

That's an awful lot of expense to get surface power equal to what the sun delivers for free.
It's a lot more than the sun delivers for free.

In northern Europe...
Northern Europe is a corner case. Ultimately, a niche with less than 20% of the world's population.


...and the same problem Northern Europe has with sunlight is also a problem for space based solar to a large degree. For a geosynchronous solar power satellite, they need a receiver on the ground about twice that of the same angular spot size as on the equator (or, if beam areal energy is the constraint, it still needs to be nearly twice as big as the equator one as the beam is more concentrated in the air than it is on the angle it hits on the ground). It also passes through almost twice as much atmosphere and is thus more sensitive to weather.
« Last Edit: 05/03/2018 12:49 am by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline alexterrell

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Re: Space Solar Power with BFR
« Reply #51 on: 05/03/2018 10:55 am »
Northern Europe has about 30-50% of the world's demand for clean energy. Partly as a result, electricity is about double the price compared to the USA. If some one does space solar power, Europe or Japan will be the initial target markets, as competing with coal and gas in the USA and hydro in Canada is not easy.

Western Europe uses about 300GW of electricity. That's enough to get going. Whilst the first Powersat is going to be very expensive (perhaps unaffordable so), subsequent ones would be a lot cheaper. 

As for Rectenna size, it would be need to be double sized at 60 degrees North, compared to the Equator. Potential sites might be Thames Estuary (52N), offshore near Copenhagen (55N), in Osaka Bay or Tokyo Bay (Japan 35N).

It might even be an idea (Musk would like this ) to ditch the solar panels and just have the rectenna receiver.  Then beam from the Sahara to New York for their morning demand, and from Arizona to London for their evening demand. But I think if you're going to put this infrastructure in orbit, you might well add the solar panels.

Offline alexterrell

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Re: Space Solar Power with BFR
« Reply #52 on: 05/03/2018 11:41 am »
Attached is a NASA study titled "Satellite Power Systems (SPS) Concept Definition Study" done by Rockwell in 1980.

Page 14 states "power output must be decreased to satisfy the 23 mW/cm2 (0.23 kW/m2) RF energy constraint in the atmosphere to avoid potential microwave interference with the D and F layers of the atmosphere." Seems to be an issue with microwave power transmission through the ionosphere.

Good study. It shows the system was feasible, with problems, with 1980s technology. It would be nice to update it to current tech.

Regarding the atmosphere:
http://www.radio-electronics.com/info/propagation/common/atmosphere.php
It seems that a high density of radiation will ionise particles, which then block radio waves. However, this can't be the whole story because most radiation is coming from the sun (1.3KW/m2), so why would a weaker microwave signal make this worse?

It does say:
Quote
The main effect of the D region is to attenuate signals that pass through it, although the level of attenuation decreases with increasing frequency.
So it might be better to go to >5GHz signal. That reduces the transmitter size, which increases the heat problems.

The efficiency chain was interesting
http://prntscr.com/jd69bu

and they reckoned 30,000 tons: http://prntscr.com/jd69zl

Even with BFR prices, that mass would need to come down a lot.


Offline Robotbeat

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Re: Space Solar Power with BFR
« Reply #53 on: 05/03/2018 12:51 pm »
Northern Europe has about 30-50% of the world's demand for clean energy. Partly as a result, electricity is about double the price compared to the USA.
The world is growing, by the end of this century demand for energy is likely to be roughly proportional to population, making northern Europe niche. And the US has cleaner energy than much of Europe, such as Germany, but much lower prices (because Germany has particularly non-optimal clean energy policy combined with low sun).

Again, Northern Europe is not an appropriate benchmark for global clean energy. And is a bad target for space solar power as well due to the high latitude.
« Last Edit: 05/03/2018 12:55 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Robotbeat

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Re: Space Solar Power with BFR
« Reply #54 on: 05/03/2018 12:53 pm »
Attached is a NASA study titled "Satellite Power Systems (SPS) Concept Definition Study" done by Rockwell in 1980.

Page 14 states "power output must be decreased to satisfy the 23 mW/cm2 (0.23 kW/m2) RF energy constraint in the atmosphere to avoid potential microwave interference with the D and F layers of the atmosphere." Seems to be an issue with microwave power transmission through the ionosphere.

Good study. It shows the system was feasible, with problems, with 1980s technology. It would be nice to update it to current tech.

Regarding the atmosphere:
http://www.radio-electronics.com/info/propagation/common/atmosphere.php
It seems that a high density of radiation will ionise particles, which then block radio waves. However, this can't be the whole story because most radiation is coming from the sun (1.3KW/m2), so why would a weaker microwave signal make this worse?

It does say:
Quote
The main effect of the D region is to attenuate signals that pass through it, although the level of attenuation decreases with increasing frequency.
So it might be better to go to >5GHz signal. That reduces the transmitter size, which increases the heat problems.

The efficiency chain was interesting
http://prntscr.com/jd69bu

and they reckoned 30,000 tons: http://prntscr.com/jd69zl

Even with BFR prices, that mass would need to come down a lot.
30,000 tons at $10/kg (BFR pricing) is just $300 million. Not bad for 4Gigawatts to the grid. The mass is fine. It isn’t the constraining factor.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline alexterrell

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Re: Space Solar Power with BFR
« Reply #55 on: 05/03/2018 04:21 pm »
Northern Europe has about 30-50% of the world's demand for clean energy. Partly as a result, electricity is about double the price compared to the USA.
The world is growing, by the end of this century demand for energy is likely to be roughly proportional to population, making northern Europe niche. And the US has cleaner energy than much of Europe, such as Germany, but much lower prices (because Germany has particularly non-optimal clean energy policy combined with low sun).

Again, Northern Europe is not an appropriate benchmark for global clean energy. And is a bad target for space solar power as well due to the high latitude.
At some point, the whole world should aim for European levels of power consumption.

Northern Europe is an excellent initial target market because of high electricity prices, an appetite for clean energy, and not much land space or sun to generate the clean energy. With the possible exception of Japan, there is no where better.

https://www.ovoenergy.com/guides/energy-guides/average-electricity-prices-kwh.html - go for anything over 20 cents per KWh.

Latitude is not problem. It just means elongating the receiver a bit.

And the US has cleaner electricity than EU countries like Poland, Malta, Latvia and Estonia.

Offline Athrithalix

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Re: Space Solar Power with BFR
« Reply #56 on: 05/04/2018 01:40 pm »
One of the most believable current proposals for bringing solar energy on a large scale to Europe is by connecting mega-grids to the MENAT (Middle East, North Africa, and Turkey) region, where huge amounts of investment and technology development are going into solar farms. Given that this is the current direction that green energy in Europe is likely to take, the question for the BFR providing us with space solar power, is can it make SSP cheaper than connecting our grids across to Morocco and Arabia?
It's not really competing with large scale solar power on the ground in Europe, as at that point it's better to use large solar farms further South than to build them in our rainy lands.

Offline tdperk

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Re: Space Solar Power with BFR
« Reply #57 on: 05/04/2018 02:26 pm »
Quote from: ElonMusk
Take any given solar cell: is it better to have on Earth or in orbit? What do you get from being in orbit? You get twice as much sun, best case.

Actually it is at minimum threefold, and with the vagaries of weather in most terrestrial locations, more like four fold.

Ironically, it is a similar multiplier to how much more efficient the energy in a battery EV like the Tesla can be used compared to the stored energy in a tank of gasoline in an IC car.

Offline tdperk

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Re: Space Solar Power with BFR
« Reply #58 on: 05/04/2018 02:27 pm »
At some point, the whole world should aim for European levels of power consumption.

Why should we endorse that relative level of poverty as a goal?

Online oldAtlas_Eguy

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Re: Space Solar Power with BFR
« Reply #59 on: 05/04/2018 05:34 pm »
The key to th business case is the amount of land used for solar cells vs rectenna to deliver the same total MWh per year or day average. The case for SSPS  is that the land usage is less because the total MWh per Km^2 over a day is higher with a rectenna than with solar cells. That is because the conversion efficiency of the rectenna to received microwaves is much higher >85% vs the conversion efficiency of solar of at peak of 40% for the best cells available but that has to be multiplied by the available sun over the day average  per year of just ~30% so the best conversion and output per m^2 for solar cells is 12% of the peak solar influx. Then add to that the battery energy storage efficiency for 66% of the energy gathered is about 85% reduces the system efficiency of solar peak energy available and delivered to the grid of 10.8%. This the best currently possible. This then for the received solar influx produces 4.5MWh of power per Km^2 of area on average per hour to the grid.

A rectenna converts at 85% and has no fluctuation in available incoming power. No battery storage. So at .23KW per m^2 that is for 1 Km^2 a value of 195 MWh of power per Km^2 of area on average per hour to the grid.

The land usage is a factor of 195/4.5 = ~43

For solar cells on surface to produce 1 GW  average output / hour requires at least 222Km^2 of area.

For rectenna on surface to produce 1GW average output /hour requires about (includes a triple amount for a protective non used or fading out power density ring surrounding the rectenna) of ~ 15 Km^2 of area.

Land on Earth is at a premium. You need to have these massive facilities as close to where the power is to be used to reduce the transmission loss through the wires. Finding 15 to 75 Km^2 (1GW to 5GW average daily output/hour) is much easier that trying to find 222 to 1,110 Km^2 (1GW to 5GW avergae daily output/hour).

Even if the costs per GWh produced is the same for ground solar and SSPS, the SSPS system will win out just because of land usage. Surface solar will still be used but will be an augmentation and not the prime power source for industry and inclement weather. The surface solar will be more of a implementation of usage on available sunward facing rooftops.

Added:
NOTE - For those worried about getting cooked the .23W/cm^2 is less than that produced by your cellphone of 1W/cm^2 next to your head.
« Last Edit: 05/04/2018 06:12 pm by oldAtlas_Eguy »

 

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