Water-to-water heat pump alternative, or still possible?

Hello,

we have been planning the house construction for some time now, and we already have the plot. Over the winter, we want to finalize everything so that everything can start in March/April 2017.

So far, we have actually been quite focused on a water-to-water heat pump. Since there is already a groundwater well (about 7 meters deep) on our plot, we took a water sample there. Today we received the sobering call from the lab: Iron: 0.79mg, Manganese 0.21mg, pH value 7.2! In addition, aggressive carbonic acid with 10mg. According to various datasheets from heat pump manufacturers, the limits are exceeded by a multiple in some cases. Due to inquiries with various installers, we are getting (as it often is with this topic, as with the rest of the house construction) dozens of different opinions. Two installers said we should just forget it altogether. Another, however, said that it can be operated absolutely problem-free with an intermediate heat exchanger. Yet another said that you can simply flush with citric acid once or twice a year. All of these gentlemen give a basically convincing and competent impression to me, so now I am stuck between three stools. I know this flushing process with citric acid. A friend does this with his heat pump about every 5 years. But he (I think) doesn’t have water as bad as ours. (he lives about 2 km away)

Now we are looking for alternatives for our house. We exclude fossil fuels, pellets, and wood. For geothermal collectors, the plot is almost too small (heated area approx. 155 m² over two floors plus basement on a 690 m² plot). How does the energy efficiency of a brine-to-water heat pump compare? A borehole drilling should actually work.

Can the thing also be used for cooling? Possibly also in connection with a ventilation system? (so not purely via the underfloor heating)

Originally, we planned to operate the heat pump in conjunction with a 5kW photovoltaic system. (The roof is ideally oriented to the south)

Thanks and best regards

Is an air-to-water heat pump not an option?
Is it very cold where you live in winter?

Why should/must it be a warm water heat pump? What do you think of a SW heat pump? This way you avoid all problems related to the components of the groundwater and basically use the same energy.

In the initial post, I already mentioned the brine-water heat pump. That would be a (at least for me) conceivable alternative. My partner tends to prefer the air-water heat pump. However, I don't like that one so much due to the somewhat higher ongoing costs, the outdoor unit, etc. Besides, I also like the idea of being able to cool a little bit with the brine-water heat pump.

What are the approximate costs for a deep drilling/brine-water heat pump for a 150m² house (two floors) plus basement?

Active cooling is also possible with an air-water heat pump. A brine-water heat pump is significantly more expensive to purchase, which under certain circumstances can take a very long time to pay off. Are there subsidies in Austria?

Funding for heat pumps is no longer available. That existed a few years ago. According to a technician from the company Viessmann, they don’t care about the water values at all because they install a screwed plate heat exchanger. I’m telling you, I’m slowly going crazy. No matter where you go, everyone tells you something different. When you finally decide on something, everyone else thinks you’re an idiot (which I don’t care about anyway). The well would apparently be really cheap to implement for us (according to the well builder). The drilling for the brine, on the other hand, would be really expensive.