Pumped storage - was two alternators

[[email protected]]

OK, so it looks like I can have multiple alternators without damage.
Now for the next part of my crazy scheme.

Looks like the property I'm buying will have a decent year-round
stream at the lowest level, with about a 25' drop across the property.
The land also has a steep gully leading into the stream that begs for
damming, and I may be able to make a nearby significant (50,000+ gal )
pumped storage pond at the top of the gully with a 60'+ drop.

I'm considering variations of the following.

Dam the stream with a small 5' dam (with a driveway on top) at the
high end of the stream to create a minimal pond that won't be
objectionable to the upstream neighbors. The area is currently
undeveloped woods and I plan to go no higher than the normal flood
stage with the pond, even though I could probably go another 20' high
without seriously affecting use of the land other than drowning some
trees.

Run a 4" pipe from the dam, buried alongside the stream for about 350'
to get the 25' drop for the normal constant powering of a small
turbine (4" pelton available for $200?) and alternator.

Run a second 2" pipe parallel that goes to a ram or hydraulic pump
that constantly fills the pumped storage pond at a slow rate. This
avoids any hammering in the first pipe.

Run another 4" pipe from the storage pond to the low spot of the
stream.

Install two 1000 watt alternators on two independent turbines.

Alternator 1 is powered by turbine 1, which has 4 jets that use the
normal run-of-stream water. Two of the jets can be valved off for
low water conditions.

Alternator 2 also has 4 jets, with two valved, but the intake can also
be valved between the stream or storage pond as needed.

Both alternators feed a small bank of six Trojan 105s. The battery
bank powers 2 2KW inverters (begin to notice the redundancy?) which
feed the house.

Now comes the fun part.

The system has electric valves that are computer controlled, a water
level sensor for both dams, metering of the batteries, alternator
outputs, usage history, and whatever other inputs are needed to
provide information to a controller program.

I can write the software that controls all of this, with the intention
of optimizing the system and reducing the strain on the batteries.

For example:
1) Normal summer day with low flow. Two jets on the main alternator
power the minimal loads and keep the batteries charged. The ram works
at filling the storage pond, and the water is allowed to build in the
stream pond. Some solar augments the system to keep the charge up in
the unlikely event that the stream goes dry.

2) Nighttime comes and the lights and tv go on. The stream alternator
goes to 4 jets to make up the increased current drain, using the
stored water at the stream pond.

3) The electric dishwasher goes on and powers on the heating element.
The second alternator kicks in as needed from the stream flow.

4) The next day, the day gets too hot for passive cooling techniques,
and an air conditioner kicks in. The second alternator then switches
the water from the storage pond instead of the stream to balance the
load. If the storage pond reaches a low water level, a warning is
given, the flow valved off, and a gasoline or biofuel powered
alternator takes over, with excess power used to pump the upper
storage pond back full during the day. At night, the gas generator
shuts down during quiet hours.

The purpose of all this is to maximize the energy extraction from the
stream, and reduce the size of the battery bank to a minimum by using
the pumped storage as a water battery.

The expense of the extra turbine/alternator and valving is offset by
reduced battery costs.

Comments?

 

[Vaughn Simon]

Run a 4" pipe from the dam, buried alongside the stream for about 350'
to get the 25' drop for the normal constant powering of a small
turbine (4" pelton available for $200?) and alternator.

I would check into friction loss in that 4" pipe before did that. (there
must be some tables somewhere) It might be far more efficient and not terribly
more expensive to go up a size or two on that pipe to reduce the water velocity
and thus the friction loss.

My other comment is KISS (Keep It Simple) (Your choice of several
possible words for the second "S")

Vaughn

 

[[email protected]]

I would check into friction loss in that 4" pipe before did that. (there
must be some tables somewhere) It might be far more efficient and not terribly
more expensive to go up a size or two on that pipe to reduce the water velocity
and thus the friction loss.

My other comment is KISS (Keep It Simple) (Your choice of several
possible words for the second "S")

Vaughn

Energyalternatives.ca has a downloadable calculator for microhydro.
4" should be more than adequate. I was initially looking at 2" and
found exactly the type of loss that you are pointing out.

Keeping it simple works great when the parameters are simple. The
reality of loads is that they don't always follow patterns that allow
simple solutions. I also have to take into account that there will be
times when we are more interested in enjoying the stream than
generating power.

 

[[email protected]]

I'm no expert but it seems to me that if you've got a stream running
year-round 24/7 then you wouldn't need all that much storage.

That would work if I went with a much larger dam and timed the turbine
to work the same way that power companies do for peak load. However,
I don't want to alienate the neighbors or run into legal problems from
flooding land that isn't mine.

Figure a battery bank large enough for a few hours to even out the load.

When talking about storage, the cost of batteries is pretty linear.
With a storage pond, however, much larger storage capacity costs
little more than the initial cost of setup, and I like having the
larger storage capability.

For instance, say you use 24kWh/day or 1kW on average. You can size
your turbine to produce 1.5 kW. When you're now using the average
of 1kW the system charges a set of batteries and when you need more
than 1kW (cooking, welding, etc) it'll get it from the batteries.

24 kwh is probably high for the example. In our all-electric house
the current month is 36 kwh/day, which includes all water heating,
cooking, heating and AC, pool pump and irrigation pump. I'm
anticipating 14 kwh or less per day because of much better insulation,
heating water with wood and gas, semi-passive cooling with cool stream
water, etc.

How big a battery bank would you need? Say your home putters along
at some 500W for 16 hours of the day (8kWh) and 2kW the remaining
8 hours (16 kWh). Your batteries would need to supply that extra
1kW for 8 hours, or 8 kWh. At 12V that 8,000Wh is some 666 Amp-hours.
Surrette sells a 683 Ah 6V battery (6CS-21PS) but even golf cart
batteries run around 220 Ah so you could run three pairs of those.

Actually it would need closer to six pair, since batteries discharged
below 50% get into deep doo-doo, so comparative set-up costs are more
similar than might be expected. Also, batteries have to be replaced
every few years at some expense, where a modular system using standard
automotive alternators can allow for replacement of them for a couple
hundred bucks or less. The storage pond itself lasts essentially
forever. Old computers are free for the asking.

The unusual and exciting situation I have is that the land is almost
ideal for this type of power storage, where most other systems are
limited to battery storage because of space and other constraints.

If you had energy efficient appliances then you could, perhaps,
reduce your electricity usage down to one third of that 24kWh/day.
You might get away with a single pair of golf cart batteries.

Anthony

Yeah, I do want to "get the lead out" as much as possible and use the
batteries more as short-term capacitive components than for heavy
energy storage.

 

[[email protected]]

Looks like the property I'm buying will have a decent year-round
stream at the lowest level, with about a 25' drop across the property.
The land also has a steep gully leading into the stream that begs for
damming, and I may be able to make a nearby significant (50,000+ gal )
pumped storage pond at the top of the gully with a 60'+ drop.

.... 9.4 kWh at 100% efficiency?

Run a second 2" pipe parallel that goes to a ram or hydraulic pump
that constantly fills the pumped storage pond at a slow rate...

How slow?

Nick

 

[[email protected]]

... 9.4 kWh at 100% efficiency?

Sounds about right. I need to get on the land and examine it more to
estimate a more exact size and height. I ballpark it at about 4
swimming pools in size.

How slow?

Off the cuff, I'm thinking that it will probably be able to fill the
pond by itself about once a month or less. However, since the gully
has its own 3 acre catchment basin, and the area gets fairly
consistent rains of about 5"/mo, that time will likely be less,
possibly even halved, depending on percolation, pond seal,
evaporation, etc.

Also, I have to see how often the stream gets to flood stage and how
long it stays there. If it does so regularly, it may pay to tap some
of that excess energy for storage. Looks like the primary catchment
area is just under 2 sq miles, with about a third of that forested, so
a major rain run-off could be quite heavy.

One interesting feature is that the stream has eroded away the
oversoil and is now down to an impervious shale/slate layer. If the
layer extends over the entire area, that bodes well for a consistant
base flow, and less losses to deeper aquifers.

 

[Bruce in Alaska]

Dam the stream with a small 5' dam (with a driveway on top) at the
high end of the stream to create a minimal pond that won't be
objectionable to the upstream neighbors. The area is currently
undeveloped woods and I plan to go no higher than the normal flood
stage with the pond, even though I could probably go another 20' high
without seriously affecting use of the land other than drowning some
trees.

Run a 4" pipe from the dam, buried alongside the stream for about 350'
to get the 25' drop for the normal constant powering of a small
turbine (4" pelton available for $200?) and alternator.

You don't say what country your in, or what the local Govt. might have
in the way of Regulations for Private Dams. Second, if you build a
road on the top of the dam, you better figure on the 100 Year Flooding
Profile for the stream, and have an overfow designed into the Dam, that
can handle a 100 Year Flood Overflow Event. If you didn't do this, and
you got a "Big Dump" and your Dam failed, you would be liable for all
downstream damage. Likely, all this would REQUIRE a complete Site
Survey by a Profesional Civil Engineer credentialed by your local Govt.
OR, you could do it "on the cheap", and just build it and have the
"Personal Liability" sitting squarely on YOU, if you figured wrong,
and something happened. Dams are not as easy to deal with as Catchments
when designing MicroHydro Power Generating Systems.

Bruce in alaska

 

[[email protected]]

You'd prefer all this to 9 1 kWh batteries?

Nick

 

[[email protected]]

You don't say what country your in, or what the local Govt. might have
in the way of Regulations for Private Dams. Second, if you build a
road on the top of the dam, you better figure on the 100 Year Flooding
Profile for the stream, and have an overfow designed into the Dam, that
can handle a 100 Year Flood Overflow Event. If you didn't do this, and
you got a "Big Dump" and your Dam failed, you would be liable for all
downstream damage. Likely, all this would REQUIRE a complete Site
Survey by a Profesional Civil Engineer credentialed by your local Govt.
OR, you could do it "on the cheap", and just build it and have the
"Personal Liability" sitting squarely on YOU, if you figured wrong,
and something happened. Dams are not as easy to deal with as Catchments
when designing MicroHydro Power Generating Systems.

Bruce in alaska

Hi Bruce,

Good points and all part of the reason I'm going with such a small
dam. Five feet total height is not much higer than some catchment
wiers, and appears to be well within the sane limits of construction.
The amount of impounded water will be minimal, the stress on the
structure will be minimal, and the chance of catastrophic failure
small even if the road washes off. Given the lay of the land, even if
the dam was instantly removed by a giant hand, the rush of water would
spread out and down to a maximum 12" tall flow even before it exited
my property, less in flood stage when the stream is wider.

Downstream has a total damage potential of two overbuilt rural highway
bridges, and one abandoned home near the stream. At two miles
downstream the branch enters a major tributary with at least 50 times
the flow, where any increased flood flow would be totally lost even in
the normal flow.

Another point to consider is that the impoundment area will start to
silt up whenever there is excess flow, and within a year or two the
quantity of impounded water will be very small indeed unless I muck it
out.

In short, I am more concerned about the quantity of water that the
pumped storage pond will be impounding and could lose in a failure,
rather than the small restriction on the stream.

Looking at aerial photos and geodesic maps, I see three other similar
dammed areas on tributaries within 3 miles, and there are about a
dozen other farm and personal fish ponds in the same area. I guess I
didn't mention that the state and county laws allow rural landowners
to do just about anything they want on their land, and there is
literally no building inspector. FWIW, the existing house on the
property would no more pass an inspection than a cardboard box full of
matches around an electric heater. This isn't one of the
over-regulated over-taxed nanny states.

 

[[email protected]]

You might be real lucky to get a
delivered flow of 10 gpm (1/3 pumped, 2/3 discharged). But time is on your
side, operating 24/7. Over a month, 10 gpm would be 7200 gal.

Must be that new math. 1 gallon per minute, times 60 minutes, times
24 hours, times 30 days = 43,200 gallons. 3.33 gallons per minute
would be 142,560 gallons. I'm only trying to get 50,000 or 60,000
gallons a month. One of us is missing something. How did you get
7200 gallons???