Backyard Aquaponics
A place to discuss aquaponics

by what Guna said in the batteries thread, i am now paranoid that the tesla batteries are a load of crap to be stayed away from, colum. Especially when they advertise 10kwh, but you can only use 2kwh of that per day (or week was it guna??)

i think floating the panels on the tanks would be a fine idea and be easy to do, simply need good water proofing and longer cable running out of the tank to pump.

Surely pumped hydro water could also be part of your AP system? why would you even need a different water source?

The Tesla 10kWh Powerwall has a lesser number of cycles in its life than the 7kWh Powerwall, so it is unlikely to last very long if you are cycling it daily, rather than weekly. The 7kW version is designed for daily cycling, but it is only a small amount of energy- not suitable for a very large energy storage unless you have lots of money to throw at it. If you have a suitable location, then pumped stored hydro is likely to be better value if you need a lot of energy stored.
You cant practically use your AP water though, it wont be anywhere sufficient volume.

If you wanted 5kW for 12-15 hours, and had a 50metre head between storages, then you'd want close to a megalitre of water.

The floating bit is easy it is dealing with the movement that is more of an issue.

There are various ways of doing it but the simplest is a French system that is modular and everything just clips together. Not the cheapest option though.

When I find the link I'll post it.



Not really. Not directly anyway. Hydro power needs a good head to be worth doing other wise the quantities of water you need to store are huge.

Found them.

http://www.ciel-et-terre.net/

thanks for the link stu.

i assumed that the system stu would be running woud be huge anyway, or atleast have the capacity to hold enough water to do both jobs at once.

Yav
This is one of Stuarts fantasies that he has not thought through very well.

All my fantasies are very well thought through.

TBH, i would rather just win tatts and buy a shed full of batteries, sounds easier.
mostly because a megalitre is a lot of water and if using tanks its gonna cost a decent amount.
also if i had 1 megalitre of water, there is no way i wouldnt find a way to add that capacity to my ap system for stability, etc. would seem like a waste to only use it for energy storage.

You could use it for energy storage and thermal stability by using a heat exchanger.

I happen to be one of the few on the forum who is prepared to tell you when I think you are wrong.

Hydro is very nice when you have a constant supply of water at head, farty little turbine is still pretty efficient.

However lets look at the stop start situation and I can't even think on what basis or regularity this will be.
On the assumption that your turbine is at your low point and that you have a minimum of 50m of water above it constantly, dont know if I am right about this but thats approx 70 psi pressure on the soft turn off valve and the turbine glands and the pipe and the couplings.
Now the pump?s. has to push over 50 m head at at least a reasonable rate, I haven't heard of your choice or price yet. Its/their own set of delivery pipe/s? control of head when switched or cut off.

Those are 2 little points in what is a fairly complex project and for what? If Gordon is correct "If you wanted 5kW for 12-15 hours, and had a 50metre head between storages, then you'd want close to a megalitre of water."

If you come in under $70k you will be lucky and it will require regular maintenance.

Not sure of details yet but you can get pump/generators. Depending on the sizing requirements same unit can do both. Alternatively appropriate valves can allow you to make use of the same mainline pipe up and down the hill.


Actually a ML @50m of head is more likely to give 2.3kW for 12 hours or 27.25kWhr



Maintenance I cant speak to but I'm assured its relatively low and the life span is all over batteries.

At a size of 1ML I doubt its worth it if the battery cost is coming in at $1200/kWh. However, it depends constructing the bottom dam is really cheap at about 5k for 3ML. The Top water storage would be much more expensive because of rock and having to bring in clay to seal the dam or the cost of building a tank. Once you start to get into the 2-3ML capacity I think it would really come into its own.

Part of the reason to have these threads is get the benefit of peoples experience. My knowledge of these systems is pretty minimal hence why I'm exploring the idea.

I think you are being unduly pessimistic with your efficiency factor there Stuart!

13l/min * 9.81 * 50 =6.4kW

@80% conversion efficiency = 5.1kW (80% should be doable with a well designed pelton wheel and PM alternator)

15 hours * 13l/min = 720kl giving you a ~30% safety margin

You can avoid a lot of hydro control gear by just using the output to charge the battery, which is much easier to regulate. Thats how I'll be doing it here with my tanks @85m head, but only with about 4kWh of storage.

Like I said I don't know much about these things.

A friend of mine who has more experience with this sort of thing said 30% while David said 20%.

Having said that I don't know where they are drawing the demarcation lines for the efficiency.

I know pump and and pipe efficiencies but I don't know generator efficiencies or electrical efficiencies.

I could take delivered power and pump water to head at 70-80% efficiency without trying too hard (good pump with large pipe). Its all the other parts I don't know enough about. Yet.

The big pumped stored hydro systems claim up around 90% efficiency on the generation side.

If you can pump at 70% and generate at 80%, you will be right in the middle of the 50-60% round trip efficiency I mentioned earlier.

I think you mean L/s.


Yeah another advantage of the fast charge ability of the Lithium batteries.

Sleep's point about the soft close on the pipe line is a good one. The water hammer on a 50m head would be pretty serious if you closed a valve too quickly.