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Got excessive PV power? Turn it to thermal

hot_rodhot_rod Posts: 11,468Member
A new pump station from Resol enables excessive PV generated power to power a resistance element and turn it into hot water for DHW or heating loads.



Bob "hot rod" Rohr
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me

Comments

  • matt_sunwaysolarmatt_sunwaysolar Posts: 61Member
    Thanks for sharing. With net-metering laws for PV installations becoming less friendly to homeowners, some markets are moving toward "self-consumption" by way of load-shifting.
    A lot of other solutions rely on batteries for storage and discharge, which is expensive. This one simply diverts excess electricity to heat, which could certainly be more valuable to a PV system owner than low net-metering payout or tax or adding batteries and controllers to existing systems.
    I haven't seen a price-point and it doesn't look like there is an installation history to prove its merit, but all in all, this is pretty cool.
  • ratioratio Posts: 2,015Member
    What does it mean that I A) noticed the heat & domestic loops share a return and B) am bothered by that?
  • hot_rodhot_rod Posts: 11,468Member
    ratio said:

    What does it mean that I A) noticed the heat & domestic loops share a return and B) am bothered by that?

    Good eye, and I don't see a source of CW into the whole system.

    Thanks for sharing. With net-metering laws for PV installations becoming less friendly to homeowners, some markets are moving toward "self-consumption" by way of load-shifting.
    A lot of other solutions rely on batteries for storage and discharge, which is expensive. This one simply diverts excess electricity to heat, which could certainly be more valuable to a PV system owner than low net-metering payout or tax or adding batteries and controllers to existing systems.
    I haven't seen a price-point and it doesn't look like there is an installation history to prove its merit, but all in all, this is pretty cool.


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • hot_rodhot_rod Posts: 11,468Member
    The editorial in this months SWE claims on May 8, a Sunday low power consumption day in Germany It was sunny, windy average 25°C. Renewable feed in to the grid was approx 90%.

    With the coal plants fired and online there was an excess and the EPEX European electricity exchange had negative prices on the spot market, basically paying as much as E.24/kWQH to dump it.

    A dilemma.. The German government is considering restricting further expansion of wind and solar and to take wind and solar generation off grid when there is over capacity.

    That may be what is driving the concept of these PV to thermal stations.

    The same is, will happen here, 2015 saw a 66% increase in residential PV installed 2.099 MW, over 2014 and the 4th consecutive year of over 50% growth. According to EIA data.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Robert O'BrienRobert O'Brien Posts: 3,119Member
    Why not just a standard heat pump water heater?
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • matt_sunwaysolarmatt_sunwaysolar Posts: 61Member
    Here is the full spec sheet:

    http://www.resol.de/Produktdokumente/11210068_FlowSol_E.monen.pdf

    Two types of units: one for DHW / one for heating(boiler water/maybe glycol?)

    As opposed to a heat pump water heater because it can interface with any (most) existing water heating/ heating unit (rather than buying a new unit when unnecessary) and also directly controls the excess production of electricity from a PV system into heat rather than sending back to the grid.

    Without knowing the price point, it's tough to try and form a full opinion. But, I think this is a pretty interesting product. "Self-consumption" for PV systems is coming in mass, so having solutions coming is good; especially if it helps the thermal guys drum up some more work.
  • hot_rodhot_rod Posts: 11,468Member
    "Self-consumption" for PV systems is coming in mass, so having solutions coming is good; especially if it helps the thermal guys drum up some more work.

    That was my thought also, with residential solar thermal off 14% or more, this would be a good way to partner with PV installers.

    Speaking of heat pump and solar, Styria, Austria is bidding a 450,000 square meter thermal array for a district heating system.

    A whooping 1,800,000 cubic meter underground storage will maintain 20- 60°C fluid temperature. Proposed to cover 38% of the heating load for Graz district customers.
    The Danish town of Vojens has a 200,000 cubic meter storage.

    Thermal powered heat pumps boost that to 85°C, when needed, then into the underground district.

    It sits next to a gas/ steam plant as a secondary source.

    This will be 3 times the size of the Danish plant, the two Danish plants have a 45 and 65% solar fraction.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • keyotekeyote Posts: 659Member
    a better solution is to build a hydrogen electrolyzer and make hydrogen gas
  • SWEISWEI Posts: 7,356Member
    Hydrogen is tricky stuff -- challenging both to transport and to store.

    Thermal storage (when used to span moderate temperature ranges) is simple, predictable, long-lived, and inexpensive (especially when you look at total life cycle costs ). It is generally not compact, lightweight, or mobile.
  • BobCBobC Posts: 4,962Member
    Some sodium materials make very good thermal storage mediums.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • SWEISWEI Posts: 7,356Member
    Ya, for higher temps -- but the containment materials tend to the exotic.
  • jumperjumper Posts: 1,336Member
    Nuts to inverters,batteries,&interconnects. Use PV to power AC directly and when house is cool enough use the electricity for stored DHW.
  • SWEISWEI Posts: 7,356Member
    Hydronics can fix this. Chill water with PV -> compressor. Dispense as needed over the course of the day (or three, if you have enough well-insulated storage.)
  • Paul48Paul48 Posts: 4,492Member
    Isn't the output of all PV panels DC? You can have micro-inverters on the panels.
  • hot_rodhot_rod Posts: 11,468Member
    Paul48 said:

    Isn't the output of all PV panels DC? You can have micro-inverters on the panels.

    I think so. The AC panels that you can buy, have the micro inverters built on the back frame.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Paul48Paul48 Posts: 4,492Member
    edited September 2016
    They're nice, but they ain't cheap. They basically double the panel cost, for something smaller than a pack of cigarettes. It's kinda comical, it seems like most of the things you need for PV are 200 and change, each. There's some things that are more, but most are 2 -change. You would think that with the Chinese market-place opening up, this stuff would be dirt cheap now. Sadly, it isn't.
  • hot_rodhot_rod Posts: 11,468Member
    Maybe aimed for the DIY market, plug and play.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • jumperjumper Posts: 1,336Member
    I was thinking about DC motor for compressor.Of course modern DC motors are ECM. That means electronics comparable to inverters. The point is that batteries and interconnects are extra expenses that retard economic viability of PV. DHW storage is much cheaper. Especially in the long run which will include replacing those stinking inverters,batteries,&interconnects.
  • Paul48Paul48 Posts: 4,492Member
    Look to concentrated solar for DHW. Making hot water and running a stirling generator at the same time. A self-contained system that automatically tracks the sun.
  • hot_rodhot_rod Posts: 11,468Member
    A Wind Solar shop not far fro me has these 12VDC elements with integrated control. Germany made, look to be good quality. They sell them mainly for keeping livestock watering tanks from freezing in the winter


    I have access to a bunch of 120W 12V Kyoceras for cheap, only 3 years in the sun.

    I'm starting a tiny home and may try these for DHW, just for the sheer simplicity compared to a fluid based thermal system. Replace the bottom element in a 30 gallon tank with this 12VDC, leave the 240V up top for boost or non sun days.


    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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