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Questions and answers

What is a linearly controlled heat generator?

These are electric heaters which can adjust the heat output over their entire output range as required. Since the available amount of energy is constantly changing, this property is of fundamental importance for photovoltaic heat generation!

Where does AC•THOR or AC ELWA-E get the excess power information from?

Either from my-PV Power Meter or from a compatible energy management system (smart home or battery storage).

Is electric space heating required for AC•THOR?

No. You can use AC•THOR also for water heating only. If a buffer storage is available, of course, the water-based space heating can be supported.

Can I combine AC•THOR with a conventional heating systems?

Yes. Other heating systems can be supported to relieve these. For example, in summer the pellet boiler or the heat pump for the hot water does not need to be started. Combined operation with heat pumps is also possible.

Is AC ELWA-E connected directly to the PV modules like ELWA?

No, it is an AC device and plugged into a standard mains socket. From this it takes only as much power as is currently available as surplus. Since there is no interconnection with the components of the photovoltaic system, it is possible to combine them with all commercially available grid-connected PV systems.

Is AC•THOR connected directly to the PV modules like ELWA?

No, it is an AC device and plugged into a standard mains socket. From this it takes only as much power as is currently available as surplus. Since there is no interconnection with the components of the photovoltaic system, it is possible to combine them with all commercially available grid-connected PV systems.

How can a system with AC•THOR and electric direct heating use less electricity from the grid than a heat pump version?

A heat pump can "only" generate heat. There is no contribution to the electrical consumers in the building. In contrast, photovoltaics gives priority to normal household electrical consumers before heat generation and thus contributes to the reduction of operating costs to the highest degree.

How can an electric direct heating have a seasonal performance factor?

JAZ EN Comparison

Just like with heat pumps, the seasonal performance factor (SPF) describes the ratio heat generation to electricity demand (without household electricity consumer). However, while a heat pump additionally receives energy from the environment, the energy for my-PV products comes from the sun. The big advantage is that electricity is now available instead of heat for energy distribution. "Cables instead of pipes" make the system much easier and less expensive. A fact that also has a significant impact on maintenance costs.

Thanks to smart excess management, AC•THOR draws less power from the public grid than heat pumps do. For all those who want to build or renovate a house, AC•THOR offers a considerable potential for savings: The building services can be installed in the smallest space and save up to 30% of the acquisition or operating costs compared to heat pumps.

Do I need a special hot water boiler or buffer tank for ELWA or AC ELWA-E?

No, the storage just needs to have a 1 1/2 inch connection. Alternatively, many tanks may also have a revision port where a commercially available adapter can be used.

When installing, observe the length of the heating elements (45 cm), as well as the area of ​​the heating-free zone (7 cm from the sealing surface) on the heating elements.

How can stratification heating be realized with ELWA and AC ELWA-E?

Stratification heating can be realized by two ELWA units. Usually one of the devices is installed in the lower third and one in the upper third of the tank. Both devices are set to the same desired temperature and communicate with each other via the DC cabling.

In the case of the AC ELWA-E, up to six units can be controlled in priority in combination with my-PV Power Meter.

Yes! »Cable instead of pipes« leads to significant savings in operation by avoiding the thermal distribution losses on a ring main. Also hygiene regulations are easier to fulfil.

What are the advantages of "cables instead of pipes"?

For new construction: Significantly lower investment costs.

For renovation: Much less interference with the building fabric.

PV yields can be used in all energy sectors of the home (electricity, heat, electromobility).

How big must the PV system be for AC•THOR?

Depending on whether only hot water has to be heated or the space heating is supported, a PV system size between 3 and 10 kWp makes sense for a detached house.

Up to which house size is AC•THOR useful?

Hot water up to 6 persons, space heating up to 150 m² (low energy standard).

Where can AC•THOR be used?

In all houses with a PV system and a hot water boiler, the PV excess can be used for domestic water heating.

Optional: In buildings with low heating demand, electrical space heating can also be supported from photovoltaics. Self-consumption maximization is the goal!

Is the building installation with AC•THOR cheap?

Yes. AC•THOR system is one of the cheapest on the market in terms of acquisition and operation. It relieves your existing heat generation system significant.

Is AC•THOR a smart home system or maybe a datalogger?

It is not. AC•THOR is sometimes misunderstood. Technically speaking, it is an AC power controller. It linearly controls the power of electrical heat sources as a function of PV energy supply and heat demand.

Is it necessary to install AC•THOR and AC ELWA-E together?

No. Both devices can independently control the power on their own.

Advantage of AC ELWA-E: It is a fully integrated solution. An extra heating element is not required. This has significant cost advantages.

Advantage of AC•THOR: Almost every electric heat generator can be linearly controlled. So also existing immersion heaters or even those with a connection thread other than 1.5 inches. In addition, AC•THOR can also infinitely control two heating elements one after the other. As a result, stratification heating with two elements can be realized at minimal costs.

Can I use AC•THOR or AC ELWA-E also without smart home or battery management?

Yes, with my-PV Power Meter. It detects in the feed-in point if excess energy is available and transmits the information to AC•THOR or AC ELWA-E.

What happens with ELWA if the power fails?

Nothing happens. The device continues to work normally. Only the optional boost-backup function is not available.

Is the installation of ELWA or AC ELWA-E in the tank complicated?

The standard 1.5 inch thread makes ELWA easy to screw into storage.

Tip This is possible even with filled memory. How to do that you will learn here (German).

Which modules can I connect directly to ELWA?

All popular poly, mono and thin film PV modules. Only the voltages and currents have to be considered!
The ELWA operates in a voltage range of 100 -360 VDC.

Tip Click here for our practical calculation tool.

What happens to the surplus with ELWA?

In an ELWA system, no power is fed into the grid. Any excess energy remains unused as in a solar thermal system. The main technical difference is that this does not result in any material fatigue compared to solar thermal energy.

In addition, the share of excess energy with ELWA is very low. Practically it is 5-8 percent. That would be about 100-150 kWh per year for a 2 kWp system, or at best 15 euros per year.

If you need an inverter, an electricity meter with meter rental, a feed-in point and the grid connection, then the additional effort is not worth it at all.


Isn’t the efficiency of solar collectors significantly higher?

Solar thermal energy is often said to have an efficiency of 80 percent. However, this is only a snapshot taken at the collector test bench (without any heat release), that means: the value has no practical relevance!

It is much more objective to compare the annual energy yields of both technologies. Well-functioning solar thermal systems with flat-plate collectors supply about 350 kWh of heat per square meter per year. A photovoltaic system with the same area earns about 200 kWh per square meter. In between there is a factor of 1.7. That means, for a typical hot water system you need 6 square meters of thermal collectors, or 10 square meters of photovoltaic modules. But this only matters if there is not enough space on the roof, because the sun is shining for free and there is no direct correlation between cost and efficiency.

Incidentally, the area factor for solar thermal energy was still 2 in 2015, another indication of how fast the technology is evolving.

What is the advantage over traditional solar thermal systems?

ELWA is not only much easier, but also much cheaper than solar thermal systems. This applies both in a single-family home and in apartment buildings. The advantages over solar thermal are multifarious:

  •     Due to the elimination of the pipes you can save up to 90% valueable copper
  •     No cost-intensive components like pumps, valves, expansion tanks, frost protection mixtures, insulations,...
  •     Photovoltaic heating even works with low solar irradiance
  •     No lossy start-up procedures (clocking, loop warm-up)
  •     Maintenance-free (frost protection)
  •     No material fatigue during system downtime
  •     Efficiency independent from system temperature
  •     More efficient at lower ambient temperatures
  •     Nearly loss-free energy transmission from the roof to the boiler
  •     Mounting in the boiler/tank quickly and not complicated, even when tank is filled
  •     Nearly no internal consumption (2W)
  •     Grid feed-in of the energy surplus instead of stagnation (with AC ELWA and AC ELWA-E)
  •     Cost development and technical development of photovoltaics are rapid
  •     ELWAs can be used decentral, thereby no distribution losses in multi-family houses. The solar energy is converted into heat right where it is needed!

my-PV GmbH
Teichstraße 43
A-4523 Neuzeug

+43 7259 39328
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