At 01:41 PM 6/25/01 +0000:
>There are 20 messages in this issue.
... (lots and lots of discussion deleted) ...

I am afraid I don't have a lot of time to spend on this topic or this list.
And few people have time to pull together bits and make a case. But I have
a suggestion to the people interested in the topic of beamed power, and
future solar power from space.

This is a _very good time_ to make the case for beamed power. If someone
thinks there is a case for a beamed power relay to help respond to
California's situation, they should put the numbers together *now*. In
fact, I suggest they post them here. Elsewhere, I have seen the comment
that a beamed power path could transmit power with 50% efficiency, vs 10%
for new land lines. Some people are taking that to Congress, and there have
been and will be more hearings. But I am not convinced. I think the
geometry is against you. I think launch costs are against you. I would
*love* someone to prove me wrong.

In Washington, there would be a *lot* of interest in high technology
alternatives to help provide power to the western US, especially ones that
would also help leverage space development. Come up with the right couple
of paragraphs, and money could flow into this arena.

Okay class, you have 3 hours on this problem. Get set.. get ready..
*Start*! (and remember, pencils down after 3 hours.. :-).

- Eric

PS. As a helpful hint for this exam, be sure to include all assumptions in
your answer. Do not ask the reader to read other messages or other articles
- you can just repeat any important information in your summary. (The
message is - don't make people work for the answer - put all the parts
together, so your short email can be forwarded to the right congressional
contacts!)

________ InternationalSpace.com _________
PO Box 60606 Washington DC 20039-0606 USA

>
> I am afraid I don't have a lot of time to spend on this topic or this list.

You have already posted a list of references, which is excellent.
I will try to review those links and see if there are any answers there
to the questions.

In the meantime, more links and more references would help.

We need source data to back up the assumptions.

> This is a _very good time_ to make the case for beamed power. If someone
> thinks there is a case for a beamed power relay to help respond to
> California's situation, they should put the numbers together *now*. In
> fact, I suggest they post them here. Elsewhere, I have seen the comment

I agree.

> that a beamed power path could transmit power with 50% efficiency, vs 10%
> for new land lines. Some people are taking that to Congress, and there have

Ouch, beamed power should get efficiencies into the 90's no ?

Land lines are only 10% ! I thought they were a lot better than that.

Where can I see source data ?

Even searching the DOE site does not give me much, there is an awful lot
of hype there.

> been and will be more hearings. But I am not convinced. I think the
> geometry is against you. I think launch costs are against you. I would
> *love* someone to prove me wrong.
>

Geometry and launch costs are the easy parts to deal with.
They are known quantities, so zero risk.
We can put those into the spreadsheets right now.

The tricky parts are:

1) How do we get the highest efficiencies ?
2) How do we overcome the PERCEIVED safety risks
3) How do we design the antennas, at least at a high level so we can put
in some
realistic performance numbers - this affects launch weight and
efficiency, two key parameters.
4) how do we do phased array control on a multi- kilometres aperture
scale (the costs are what ?)
5) How do we deploy flimsy kilometres sized structures in space (R&D
cost) ?
6) How do we control and steer flimsy kilometre size structures in space
(R&D cost) ?

Numbers in those areas right now are rather vague.

> In Washington, there would be a *lot* of interest in high technology
> alternatives to help provide power to the western US, especially ones that
> would also help leverage space development. Come up with the right couple
> of paragraphs, and money could flow into this arena.
>
> Okay class, you have 3 hours on this problem. Get set.. get ready..
> *Start*! (and remember, pencils down after 3 hours.. :-).
>

>From my perspective it is a needle and haystack problem.

I do not have the data, and I do not know where to find the data.

Assistance would be appreciated.

Cheers,

CR.

Browsing the eia.doe.gov led me to home in on the situation surrounding "Path 15".

Currently the biggest choke point for the California grid is "Path 15",
a 90 mile ( 144 km ) stretch between Gates and Los Banos,
linking northern and southern California.

Then I found an article from the LA Times which has some interesting data points.

http://www.latimes.com/business/reports/power/lat_lines010131.htm

IT says that to add a third power line at Path 15 would cost $200 million.

Then, according to:

http://www.caiso.com/docs/2001/05/11/2001051110134222663.pdf

the Path-15 upgrade will increase capacity by 5 GW

I am not sure that the $200 million applies directly to the 5 GW upgrade,
I have no found a source which contains both numbers together.

But assuming they do,then we can derive a per kilometre capital cost as follows:-

$200M / ( 144km * 5GW ) => $278,000 per ( Gw.km)

Hence, to build a line for 5 GW over 720 km would cost $ 1 billion

A proper business evluation needs to figure a life cycle cost, which
would have to include operations costs (space versus terrestrial) as
well as the extra R&D cost for microwave transmission.

An interesting quote:-

" Expansion has been discouraged in part because...[snip]...
electricity is an interstate commodity, grid operations are
overseen by the Federal Energy Regulatory Commission, which
restricts the profit that utilities make on new transmission projects to
an annual average of 9% on investment. Such returns pale in
comparison with the 15% to 20% utilities can earn on other,
unregulated investments."

> Elsewhere, I have seen the comment that a beamed power path could transmit

> power with 50% efficiency, vs 10% for new land lines.

The figures I have from www.permanent.com give a DC to DC efficiency
per leg of 61% (from a DOE report). That would give a round trip
earth-orbit-earth of 0.61*0.61 = 0.37 = 37%. Based on my knowledge of
physics and electronics, the numbers seem sound.

37% isn't too bad.

> Some people are

> taking that to Congress, and there have been and will be more hearings.

> I think the geometry is against you.

The geometry doesn't matter except insofar as it pushes up the size
of the antennas. The energy isn't lost due to the geometry- its lost
due to conversion.

> I think launch costs are against you.

This one atleast is improving. Launch costs have come down recently-
there is now an oversupply of launch capacity. The costs are a factor
of 4 lower than when the studies were first done. A considerable
amount of the costs is in the launch costs. Also, a large order for
launch can get the costs down further due to scaling laws.

> In Washington, there would be a *lot* of interest in high technology
> alternatives to help provide power to the western US, especially ones that
> would also help leverage space development. Come up with the right couple
> of paragraphs, and money could flow into this arena.

The other unique advantages for this system include:

- more than one electricity provider can be used; this has
political advantages in that it is difficult for any state to
run out of electricity and it reduces the monopolies that tend
to form.

- cheaper electricity to start with- any state with the cheapest
electricity can be used to beam power up to the satellite. Electricity
can be chosen for its enviromental friendliness, or targetting a
particular favoured supplier.

- different states can be used across the day to provide electricity
e.g. the east coast states can provide electricity to the west coast
after they have moved off their peak usage; and vice versa- the
west coast can power the east coast with their spare capacity
in the east coast's morning before the west coast wakes up.

- The costs of the electricity are independent of distance from
the supplier. Sending the electricity across the whole country has
exactly the same losses as 5 miles.

> Okay class, you have 3 hours on this problem. Get set.. get ready..
> *Start*! (and remember, pencils down after 3 hours.. :-).
>
> - Eric

> ________ InternationalSpace.com _________
> PO Box 60606 Washington DC 20039-0606 USA

civilization?"

> Then, according to:
>
> http://www.caiso.com/docs/2001/05/11/2001051110134222663.pdf
>
> the Path-15 upgrade will increase capacity by 5 GW

Note that that's TO not BY. It says:

"... is estimate to increase the non simultaneous rating on path 15
to 5000-5500 Mw..."

If you read higher it says that the link is already running at
3750Mw. Therefore they are adding ~1.25 Gw for 200 million or so.

Hence, to build a line for 5 GW over 720 km would cost more like
$4 billion. And in fact it might be much more than that. This
is an upgrade to an existing system- they may be able to reuse
a lot of equipment, pylons etc.

Still, on the powersat side of the equation what does the worst quality
land you can find cost per square kilometer in California?

civilization?"

>>>37% isn't too bad.>>>>

37% is pretty awful. You are losing almost 2/3rds of your power. A
conversion efficiency this low casts a serious shadow over economic
viability. Didn't O'neill predict a conversion efficiency of up to 90%?

Tony

Sign up for FREE and learn how to use your computer to create multiple
income streams, from the comfort of your own home.

The 90% was for the conversion of microwaves to electricity at the rectenna, and didn't include the conversion ofelectricity to microwaves at the transmitting antenna. That said, 37% still sounds a bit low to me.

Regards,

Mike Combs

>>>37% isn't too bad.>>>>

37% is pretty awful. You are losing almost 2/3rds of your power. A
conversion efficiency this low casts a serious shadow over economic
viability. Didn't O'neill predict a conversion efficiency of up to 90%?

Some additional thoughts...

Peak powerloads are at different times throughout the world
Most power generation techniques are most efficient producing energy at a
constant rate
Many 'alternative' energy sources must be located where the energy is
available and is often not located near current population centers.

Thus this would allow power to be generated at the peak operating efficiency
for the power plant, with the production facility located either remotely
(so less concern about nuclear near a city... and the ability to harvest
wind or geothermal where it is abundant...)

Each powerplant would be more profitable, because the energy usage could be
maintained to almost constant. Also, they would have much less dependence
on expensive emergency energy production.

Tom M.
TomM@...

>>>>37% isn't too bad.>>>>
>>>>
>
> 37% is pretty awful. You are losing almost 2/3rds of your power. A
> conversion efficiency this low casts a serious shadow over economic
> viability.

It's not quite as bad as it sounds in fact.

Don't forget this would only apply to earth-orbit-earth applications,
and 37% isn't awful if you have really cheap electricity. Cars are only
15% efficient by comparison... electricity generators are never more
than 80% efficient, and some are more like 50%. If you can use energy
from the other side of the country you may be able to tap into Niagara
falls during their night or something- that doesn't actually cost
anything to produce.

> Tony

civilization?"

> The 90% was for the conversion of microwaves to electricity at the
> rectenna, and didn't include the conversion of electricity to microwaves
> at the transmitting antenna. That said, 37% still sounds a bit low to me.

Check out the diagram at: http://www.permanent.com/p-sps-tc.htm

> Mike Combs

civilization?"

> At 01:41 PM 6/25/01 +0000:
> Elsewhere, I have seen the comment that a beamed power path could transmit

> power with 50% efficiency, vs 10%
> for new land lines.

Actually from the impression I get from the web, land lines
aren't 10% efficient, they are 90% efficient. Still, beamed
power has very unique advantages; efficiency isn't necessarily
everything.

civilization?"

>

> Still, on the powersat side of the equation what does the worst quality
> land you can find cost per square kilometer in California?
>

Not researched recently. Desert land costs practically nothing.

But in northern California, the big market, it is different, not much
cheap land, except perhaps desert east of Sacramento. If the rectennas
are too remote from the market, then ground transmission costs will
start to erode the benefit.

Buying land for recetennas is not necessary. They can be dual-used
with agriculture (and other purposes),
we would negotiate leases with farmers, for them it would be a
windfall. A lot cheaper than buying the land outright.

The ground rectennas would be mesh, transparent to sunlight.

Cheers,

CR.

The 90% was for the conversion of microwaves to electricity at the
rectenna, and didn't include the conversion of electricity to
microwaves at the transmitting antenna. That said, 37% still sounds a
bit low to me.
=============

61% efficiency at the spacecraft is unacceptably low.

We simply cannot feasibly dissipate that much waste heat.

We must have efficiencies in the 90's for the space segment to be
feasible.
The high 90's.

Otherwise, our only hope would be to look at microwave reflectors rather
than re-transmitters. This doubles the path length, which makes the
geometry even more difficult, the rectenna would have to be double the
diameter.

>
> Some additional thoughts...
>
> Peak powerloads are at different times throughout the world

And they also vary with time of year and time of day.

> Most power generation techniques are most efficient producing energy at a
> constant rate

True for fossil fuels and nuclear, but not true for renewables.

This makes matching supply with demand even more complicated.

>
> Thus this would allow power to be generated at the peak operating efficiency
> for the power plant, with the production facility located either remotely
> (so less concern about nuclear near a city... and the ability to harvest
> wind or geothermal where it is abundant...)
>

And WHEN it is abundant. And WHEN and WHERE it is needed.

I can envisage a single orbital relay station feeding several
recetennas. The power to each recetenna is varied as demand rises and
falls. When averaged across an entire hemisphere, this could average
to be close to constant.

>>>>Check out the diagram at: http://www.permanent.com/p-sps-tc.htm>>>>

Thanks. When you factor in all of the losses, you get a total efficiency
of 56%, between the generation of electric power at the solar array and its
final use on Earth. I could live with that. It seems likely that many power
hugry industries, like aluminium factories, may choose to locate themselves
close to the rectena, in order to factor out transmission costs.

Tony

Sign up for FREE and learn how to use your computer to create multiple
income streams, from the comfort of your own home.

After all of the conversions, it comes to 38.5% efficiency

here are the numbers and calculations

Grid 0.97
DC to RF 0.85
Antenna 0.98
Atmosphere 0.98
Energy Collection 0.88
RF to DC 0.89
DC to RF 0.85
Antenna 0.98
Atmosphere 0.98
Energy Collection 0.88
RF to DC 0.89
Grid .97

=.97*.85*.98*.98*.88*.89*.85*.98*.98*.88*.89*.97
=.385 = 38.5%

>
> Don't forget this would only apply to earth-orbit-earth applications,
> and 37% isn't awful if you have really cheap electricity. Cars are only

But the problem is the space segment.

For these kinds of dissipation levels, the radiators required would
weigh several times more than the rest of the spacecraft combined, and
would blow away any hope of viability.

CR.

When David Criswell promotes his lunar solar power scheme, his proposed solution to the fact that the moon can only see one side of the Earth at a time is microwave reflectors in Earth orbit, which he points out would be orders of magnitude less complicated and lighter than SPS. At first I took it for granted we were talking microwave reflectors in orbit, but on looking closer, I see we're discussing actual power relays. Why aren't we just talking reflectors, since Criswell seems to think they can be made to work?

Regards,

Mike Combs

Does the statement, "The ground rectennas would be mesh, transparent to
sunlight" imply a particular upper bound on the transmission frequency
chosen?

Ron Menich

Charles
Number 135)
06/27/01
10:46 AM
Please
respond to
ssi_list

...
Buying land for recetennas is not necessary. They can be dual-used
with agriculture (and other purposes),
we would negotiate leases with farmers, for them it would be a
windfall. A lot cheaper than buying the land outright.

The ground rectennas would be mesh, transparent to sunlight.

Cheers,

CR.
...

If using a reflector, then we can eliminate the RF to DC and DC to RF
conversion in the middle...

That puts us at 50.8% efficiency... instead of 38.5% for the relay...

Tom M.
TomM@...

>
>>Don't forget this would only apply to earth-orbit-earth applications,
>>and 37% isn't awful if you have really cheap electricity. Cars are only
> But the problem is the space segment.
>
> For these kinds of dissipation levels, the radiators required would
> weigh several times more than the rest of the spacecraft combined, and
> would blow away any hope of viability.

It might be possible to avoid going through DC on the spacecraft side-
that would greatly improve efficiency and reduce power dissipation
needed; but I'd need to think more about how you could do that.

> CR.
>

civilization?"

> Does the statement, "The ground rectennas would be mesh, transparent to
> sunlight" imply a particular upper bound on the transmission frequency
> chosen?

Yes, but not practically. Frequencies above 5 Ghz or so get attenuated
by the atmosphere anyway, and the wavelength at that frequency is
about 5cm.

The deal with mesh is that it behaves more or less the same as sheet
material, provided the size of the meshing is smaller than the wavelength.

> Ron Menich

civilization?"

>If using a reflector, then we can eliminate the RF to DC and DC to RF
>conversion in the middle...
>
>That puts us at 50.8% efficiency... instead of 38.5% for the relay...
>
>Tom M.
>TomM@...

You need to add in a loss due to angle of the reflector. When the
reflector is not perfectly perpendicular to the incomeing wavefront
there is a power loss due to phase shift of the wave as each peice
of the wave front gets to the reflector. Power =K (sin(pi(L/wavelength)sin(angle))/(pi(L/wavelength)sin(angle)))squared.
Where L is the length of the reflector. If you think of the reflector
as rotating around one end of the reflector. If the distance that
the other end makes from perpendicular is equal to the wavelength
there is complete cancelation of the signal.

A reflector is going to act like a solar sail. Station keeping due
to momentum transfer will have to be calculated. The relay should
have the same problem. I don't know if the momentum transfer would
be signficant.

Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)

> A reflector is going to act like a solar sail. Station keeping due
> to momentum transfer will have to be calculated. The relay should
> have the same problem. I don't know if the momentum transfer would
> be signficant.
>

Is it possible that we could use the reflector to do more than just
passively reflect the beam? After all, it's floating in orbit anyway.
Why not have it collect solar energy of it's own to add as a "boost" to
the energy it's reflecting? Sort of an energy from orbit/energy to orbit
hybrid. I can see two issues with this: 1) increased mass of the
reflector being launched into orbit, and 2) keeping the two energy waves
from interfering with each other. But is this an option to consider?

--Justin

A reflector is going to act like a solar sail. Station keeping due
to momentum transfer will have to be calculated. The relay should
have the same problem. I don't know if the momentum transfer would
be signficant. I hope Criswell is talking to Robert Forward, who's something of an expert on pushing around light, wire meshes with microwave beams. (Or Leik Myrabo, who's done actual demos on this.)

Regards,

Mike Combs