Hot Water with Hydro

A passive solar panel would probably be way better than a ≤ 500W electrical heater.

Yes, and that may enter into the equation, but I need some hard numbers on the hydro. Also, the sun often doesn't shine when hydronic heating is most desired.

What is your definition of "hydro"? The reason I am asking is that the first thing I think of is "hydroelectric". However, from the context of your post, this doesn't seem to be the case.

So, what does "hydro" mean in your case?

Additionally, is hydronic even a word? Please enlighten me!

Yes, "hydronic" is a standard word (in my MW9C, anyway), as well as a common trade term for heating systems with circulating water as the heat transport medium (e.g., in-floor "radiant" systems).

Sorry for the confusion. Hydro does, in fact, mean hydro-electric (specifically micro-hydro) in my context. 'Hydronics' is the use of circulating water for heating or cooling.

So, your setup looks like this?

Basically, yes.

For simplicity: what temperature change over time can I expect from 500 watts into about 50 gallons of water in a well insulated container?

Thanks. That's for what I was looking.

There used to be systems with water power for heating where there was no electricity. The turbine turned something (paddles or whatever) in heavy oil or molasses and the heavy oil or molasses heated up because of its viscosity and friction. If heat is all you want, and the water power is near the house, that sounds like the way to go.

500W is a little anemic. About half a hair dryer's worth of heating power. '

Do you think half a hairdryer would heat the space and keep it that way?

What is the electrical power requirement for a Hydronic heating system of this size?

Your power generating system needs to be dimensioned to suit the load not the other way around.

Right "half a hair dryer" is not much for a radiant floor heating system. And I see it a challenge to heat a house - but not impossible. If the 500 Watts are there for 24Hours we get 12KWh in electrical energy - that is exactly what the heatpump in my 1600 sqfoot house requires on a non-sunny day with - 10 deg.C external temperature.

But directly to use the energy and to heat up water in the storage tank should be possible as the energy is continuously available. If once the water is heated up by grid power - I have the feeling that a constantly available 500W heater could maintain the temperature in the house - we have available 12kWh! And with an additional siupport by a 70sqf solar heater panel - the house is warm.

But the hydro power voltage is fluctuating so this seems not to be right way to sove the issue. But to use an inverter and constantly charge a battery bank with the available energy is possible. Then use a air - water Heatpump with a working ratio of 1:3 (1kW electrical in - 3 kW thermal out) this could be a feasible way to heat a house if locally the minus degrees in Winter are not too low. This way you can easily cover-up for the losses of the storage system or the losses due to the circulation pump. Or you have to use the option with an electrical backup heater in the watertank to support during really low temperature days.

And consider a syphonic support of the heating system via a solar heating panel of 70sqfeet on a sunny -10deg. winterday bring at a location of 48 deg.North around 11kWh thermal.

You could also consider to make use of the "hydro potential " to use this heatsource then the working figure of the water -water heatpump will be close to constant - if the water is always running and not freezing and then 500W are a lot.

Technically this is all feasible but it depends also on the house construction (Heatlosses) and the money! to implement it.

Greetings

The 1600 sq.ft. house is new and well insulated as per California building codes. The insulated slab already has the piping for hydronics. My feeling is that 500 watts is too little to rely upon as a sole heat source. As for voltage fluctuations Outback makes a charge controller which can deliver a constant voltage... All this aside, my recomendation for this client will be a solar water panel coupled with a pre-heated water tank heated as a diversion load from the hydro. So the hydro would be supplying power to batteries to inverter to house. Along with the solar hot water and hydro a small LPG on demand heater will bring the water to proper temp. The object of my question was not so much "will this work" as "how much can I expect from this marginal setup"... Also, there is a woodstove, but they didn't want to rely on that. Thanks for the reply.

I agree. 500 watts is a little small, but your analogy is not accurate. Water is much better store of heat energy than air and I can supply it 24 hours a day... Also, I am adapting the possible power generation to a system already in place, so I am just exploring the possibilities. Grid electricity is available, along with solar and propane... see response below. Thanks for the reply.

Some hot water tanks have two heating elements installed, high and low and the thermostat switches between them as required to extend the capacity of the tank and system in response to heavy use.

Here is my idea: Hook the lower element of such a tank directly into the generator output and connect the upper element only to the powergrid via the thermostat with a low'ish setpoint that can act as backup heat if required. The power output from the generator is too low to require any controls or conversion other than an ON/OFF switch and the only precaution necessary is to ensure the electrical resistance in the heating element is far greater than the resistance in the supply cabling from the generator in order to get most of the heat inside the tank. (If necessary replace the original heating element with a lower rated one)

It may even be possible to get the system to work with thermo syphoning only, but plan for a small circulating pump anyway.

How much heat loss? Double pane windows? Heavy insulation? Small house? Floor heating is very comfortable, but it wouldn't take much heat loss to neutralize it.

1600 sq.ft. new house built per CA building codes.

If you use the 500 watts to run a ground source heat pump (geothermal) you can leverage the 500 watts to 2000 watts of energy, 1500 from the ground and the original 500 in electricity. The problem is finding a heat pump small enough to run on 500 watts, might be able to put something together from small refrigerator parts.

Thanks, but retrofitting for geothermal is not an option.

yes the size of the heat pump is the catch - this you can only get in most cases only via three phase AC - so you need the battery inverter combination. The smalles Heatpump I found is 6kW (mine has 9kW - it was designed to be a 11kW unit by the esxperts but when it came to space issues we found that 9kW is anyway enough - and the last winter which had a long period of nasty cold & days confirmed this. So solar did not contribute.

Coils into a fire place I would not do - there are already here in Germany wood stoves available which have the coil build in and the required waterpiping /pump. But we decided to go with a conventional stove - as we tab already the sun via the solar heate system. THe water casette stove needs electricity to cater for the heat transfer to the floor heating system - which might not be available when the big multies cause blackouts etc. So we can heat the house even without electricity.

REgards

I'm not sure that we can answer your question. It seems to me that you are wanting to know how warm the floor is going to get, how fast, and the resulting room temperature. Tornado gives the answer given no heat losses through insulation. But, heat losses are the point of this whole exercise. You want most of the heat to be lost into the room. The insulation of the slab, the thermal mass of the slab (enormous), the thermal conductivity of the floor covering (unless it's bare concrete), the insulation of the room, and the rate of air exchange all come into play. You really need to know the heat load of the room to calculate the impact of the floor heating.

When you first start up the system, a lot of the heat will be going into heating the slab, so your floor temperature will rise slowly. One of the strategies used in traditional solar heating, is to store heat in a rock wall during the day to radiate out overnight. No matter what source you end up using to maintain the heat load, you will need to initially warm up the system. An auxillary heater is a good idea for this. It will also be helpfull during an especially cold day as a back up.

Is there a fireplace in the house? I have never tried to harvest heat from a fireplace using water, but it may work to have a coil against the back wall of the fireplace for some of your water to circulate through.

I really like the idea of harvesting geothermal heat.

The most efficient system may be a combination of sources, but controls may be a bear to design. Good luck.