Photovoltaic in ecogîte: small question energy storage

[Grelinette]

From time to time I volunteer with an association that has created a completely autonomous eco-lodging.
( http://educ-envir.org/~loubatas/ )

Right now, in the south, we have a permanent and very strong sun. Conversely, the groups accommodated in the eco-lodging consume less energy: no heating, cold showers, little lighting, etc.
Suddenly the batteries are all full and the photovoltaic panels produce without interest.

What would be interesting to do so that this energy produced can be exploited in one way or another (and mainly in summer)?
(knowing that the eco-lodging is not connected to the EDF network and that there is already a large part of the eco-lodging filled with batteries)

Do you have any interesting ideas for using this energy?

Some tracks ... :

- a non-polluting air conditioning system for the eco-lodging (does it exist?)
- store energy in the form of heat
- operate any useful device
- maybe equip the ecogite with electric carts
- why not a battery charging station
- ...

It is paradoxical and even distressing to note that in summer the production of electricity is maximum while consumption is minimal, and the reverse in winter. The worst thing is that when there are many people and little electricity production, it is sometimes necessary to use a generator to compensate for the lack of electricity!

[minguinhirigue]

The heat storage and the air conditioning system would be in your case a simple water circuit cooling the rooms and storing low temperature heat in the basement? But it is very heavy work in renovation ...

Maybe a pump to oxygenate basins?

Otherwise, it may be the best time to do work with power tools ...

Seriously, I only see electric cars or bikes ... It can be an opportunity for easy walks ...

[Grelinette]

I hadn't thought about it but ultimately the idea of ​​electric bikes seems great and well suited to the concept of the eco-lodging!

In addition, "over-produced" electricity can keep a small stock of bicycle batteries so that electric bikes are always operational!

[elephant]

As I suppose that you do not receive ONLY spartans, I think that the cheapest would be to produce domestic hot water.
But beware, you must limit the intake (timer) so that there is current to light up in the evening.

[Grelinette]

... the cheapest would be to produce domestic hot water.

In this heat wave season (and increased electricity production) it is not very interesting because we take more cold showers than hot, and there is no heating in the building!

On the other hand a new idea was suggested to me which seems interesting (with that of bikes and other electric vehicles): use this surplus of electric production to activate a pump which will put water in a tank in height.

It is all the more interesting that the relief lends itself well to it and that in addition it makes it possible to store a good reserve of water against the risks of fire. In addition there is an on-site borehole already powered by solar panels; it would be a kind of energy "overflow" that converts electricity into potential energy stored in water.

This water stored in height by gravity will drive a turbine which will produce electricity when the electric consumption is higher than the production, for example in the evening or after several days without sun.
This technique would make it possible to recover more than 70% of energy thus stored.

It is almost a perpetual movement if the water coming down is stored in a lower tank, ready to be raised!

It remains to find a solution so that it works in winter when the water freezes.

[minguinhirigue]

Hydraulic storage is indeed a nice solution, maybe it needs to be sized so that it is empty when it freezes?

[elephant]

Well, before you dream:

1) you still need hot water to wash the dishes, right?
2) capacity of the gîte in people
3) drop
4) installed photovoltaic power (in peak Watts and battery capacity)
5) location (department + altitude)

I have some concerns about the cost of this turbine.

Indeed, this is a solution: we have 2 power plants like that in Belgium, but they are monsters that cost billions

[Grelinette]

1) you still need hot water to wash the dishes, right?
2) capacity of the gîte in people
3) drop
4) installed photovoltaic power (in peak Watts and battery capacity)
5) location (department + altitude)

I have some concerns about the cost of this turbine.

Indeed, this is a solution: we have 2 power plants like that in Belgium, but they are monsters that cost billions

Oula friend, it's not a question of producing gigawatts to make coffee or dishes!
My question comes from this observation full of common sense:

- the weather is nice and warm = we produce a lot and we consume little (and the batteries recharge quickly and stay full)

- the weather is not nice and cold = we produce little or nothing, and we consume a lot ... and the worst is that it is sometimes necessary to use a diesel generator to get current!

In short, how to linearize all this?

The cottage located under the great sun of Provence, on the hillside with a lot of elevation and can accommodate from 20 to 35 people.

In summer, most take a cold shower, and even if there are dishes and coffee, the electricity consumption is minimal compared to the production capacity of PV panels.


To come back to the turbine, it seems to me that it should not be much more difficult to design than a wind turbine, and perhaps even that the electrical production apparatus can be the same as for a wind turbine.

Install a high-level tank type large self-supporting above-ground swimming pool (20 to 30 m3)
(bathers are optional but do not bring more energy, it's just more aesthetic )

So to sum up: summer, during a period of great sun, when the batteries of the gîte are full and the PV panels continue to produce, a system switches over to a pump which fills the water reserve at height.

If the batteries are empty, an automatic or manual valve will open the reserve and drive a turbine which will replace or complement the solar panels ...
(note that the water that comes down will not only be filtered to serve for dishes, ... or coffee, but will also be recovered in another reserve below: it's perpetual movement ... CQFD!

Apart from the turbine technology that remains to be developed, what do you think of such an installation?

[Christophe]

(bathers are optional but do not bring more energy, it's just more aesthetic )

Oh no, a human body is 60 to 150W of heat loss (70-80 W on average for a man) ... when you swim "well" you must exceed 150W ... and therefore you heat the pool well !

Apart from the turbine technology that remains to be developed, what do you think of such an installation?

Are you serious about this idea of ​​hydraulic pumping? Let's take a concrete example.

Let's say that your environment and energy potential allows you to pump 30 m3 to 100 m (I voluntarily take a figure of high height).

For each kg of water pumped, you will therefore accumulate a potential energy of: 1 * g * h in joules or 1 * 9.81 * 100 = 1 kJ say. I neglect the balance of pumping because you will be in excess of energy ... what matters is what we can recover.

Or 1 kJ / kg (cool it's easy to remember) at 100 m.

So 30 L = 000 kJ = 30 MJ

By taking a turbine efficiency of 60% and alternator of 80% (pelton turbine seen the fall), you will have, with 30 m3, an electrical energy of 30 * 0.6 * 0.8 = 14.4 say 15 MJ.

Or 1 kWh = 1000 J for one hour, i.e. 3.6 MJ.

Your system will therefore store the equivalent of 15 / 3.6 = 4.2 kWh
You will tell me that it is not so bad yes, but it is for 100 m of pumping!

If you pump at 20 m, you must divide this potential, if all goes well, by 5 ... or less than 1 kWh of storage for 30 m3 stored.

Unless I am mistaken in reasoning, I think that we must really weigh the pros and cons of such a solution and we have not even talked about the costs yet ...

Would that compare to the cost of storing 1kWh in a cyclic solar battery?

[minguinhirigue]

Inertial storage is interesting but it does not actually work in a small basin (<100 M3), as Christophe points out. This makes it difficult ...