Hot Water from Solar PV Panels

Hot Water from Solar PV Panels – an obvious choice

Many households prefer not to export their surplus electricity to the grid. In Ireland there is no payment for exported power, and it is simple and easy to use this surplus to provide solar hot water.

You can install a PV system to heat water for a lower cost than most solar tube systems, with the advantage that there is no need to change the cylinder, no water system running up to the loft requiring regular maintenance or anti- freeze.

In the UK and elsewhere, numerous diversion devices have been developed to use your surplus electricity from a solar panel or wind turbine to heat water in the immersion cylinder. These different systems have pros and cons. Please talk to us about which unit might suit your situation.

Hot Water System 1
Cable clamp goes around grid feed to Consumer Unit

A clamp sensor is put around a cable from your mains power coming into the consumer unit. When you are exporting more than about 50 watts of power, it tells the unit to start using power in the immersion heater.

Effectively, a dimmer switch on your immersion is then turned up and down to use your surplus solar electricity, providing hot water without using any electricity from the grid.

If you need hot water on a dull day, you can still use your regular boiler or immersion to provide this.

Solartricity Apollo Gem
Apollo Gem
Immersun Hot Water System 2
Immersun Hot Water System
Solartricity Solic 200
Solic 200

We have four models on offer;

  • Immersun – very precise management of up to two loads. This unit is a proportional controller that does not affect the quality of the grid in any way, whereas the units below may cause flicker or some noise. A remote transmitter can also be used to transmit data to a website so you can see the production of your PV system, and also know how much surplus energy is being diverted to hot water.
  • Apollo Gem - Can run two separate heating loads and switch from one to the other, so you can prioritize a top-of-cylinder immersion and then have a second lower immersion kick in. This unit also comes with a screen so you can monitor energy being saved. A temperature probe can also be added so that the unit displays water temperature. This unit may cause some flicker of light bulbs if old-fashioned filament bulbs are still in use.
  • Apollo Gem Lite – Runs one load, but comes with wireless communication between the unit and the sensor. This makes it easier for retrofitting if you want the unit near the immersion. This unit may cause some flicker of light bulbs if old-fashioned filament bulbs are still in use.
  • Solic – Uses phase angle to provide very precise load switching. This unit may produce some electrical noise in sensitive equipment such as ham radio or X10 transmitters.
Immersun Hot Water System
Immersun Hot Water System
Solartricity temperature probe
Temperature sensor for Apollo Gem

Please contact us to discuss which unit suits your situation.

System Schematic

Hot Water System Schematic
Hot Water System Schematic

Example winter’s day log of a hot water diversion system:

Immersun System

This is the log from the Immersun website for a 2.6Kw system working on a bright day in February.

On the left, at the time, the system was producing 1028 watts at that moment in time. 717 watts was being sent to the immersion and 244 watts was being used in the house. A nominal 67 watts was being sent to the grid at that time.

On the right, we can see a graph of solar production peaking at 1.6kw and below that, data on consumption and diversion to hot water.

During the day, 9.7 KwHrs was produced from solar, 8.2KwHrs consumed, 6.6KwHrs used to heat water and 5.5kwHrs imported from the grid.

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