Power-to-Heat - ratiotherm Smart Energy Systems

Q: Is power-to-heat worthwhile for private households?

Yes. Power to Heat is worthwhile for private households. Power to Heat is particularly interesting for households that are no longer eligible for the EEG feed-in tariff. Otherwise, there is no longer any profit to be made, either in terms of energy or costs. The investment costs remain manageable even when combined with heating systems based on heating oil or gas. The technical effort is also straightforward, as are the investment costs. Power to Heat can be combined with any type of heating system.

Q: What exactly is the EEG feed-in tariff?

EEG is the abbreviation for the Renewable Energy Sources Act (Erneuerbare-Energien-Gesetz). Consumers who generate electricity from photovoltaics and feed it into the public power grid receive a feed-in tariff under the EEG. The EEG was an incentive for private and commercial customers to install photovoltaic systems in their homes. At the beginning of the 2000s, the feed-in tariffs were, of course, considerably higher than they are today. Now, after around 20 years, consumers with photovoltaic systems are wondering what will happen when the EEG expires. This is where Power to Heat comes in. Use your own electricity to generate heat. Save oil, gas, and wood.

Q: Why is Power to Heat an environmentally friendly storage method?

Power to Heat is an environmentally friendly storage method because it uses a thermal battery. Our Oskar° stratified storage tank converts solar energy and can store it for long periods of time. The environmentally friendly aspect lies primarily in the simple transfer of energy. Heat is a luxury commodity. Power to Heat technology saves solar energy that would otherwise be lost by converting it into heat, thus generating an attractive new source of energy. You can use surplus energy from summer days at a later time. The more energy is generated and stored, the longer it can be used at a later date. Private households are faced with a decision: battery or Power to Heat. Batteries are often the more expensive option. Power to Heat means using inexpensive storage. In addition, Power to Heat technology with buffer storage can store energy, whereas a battery cannot.

Q: Is Power to Heat with a heating element or a heat pump the better option?

In Verbindung mit Power to Heat ist die Wärmpumpe das effizientere Medium als der Heizstab. Sie verwandelt den gleichen Anteil an Strom in mehr thermische Energie als ein Heizstab. Während die Umwandlung beim Heizstab bei 1:1 liegt, schafft die Wärmepumpe beispielsweise 10 Kilowattstunden Strom in 30-40 Kilowattstunden thermische Energie umzuwandeln, also das 3-4 Fache. Allerdings ist der Heizstab in der Anschaffung deutlich günstiger als eine Wärmepumpe. Er wird oft als Aufrüstung verwendet. Eine Wärmepumpe ist vorzugweise bei einem generellen Energie-Wechsel von alten auf erneuerbare Energien sinnvoll.

Power conversion for greater efficiency

The term “Power-to-Heat” or “Power-2-Heat,” abbreviated as p2h or PtH, refers to the conversion of renewable electricity generated from sources such as photovoltaics (PV), wind energy, or biogas into heat. This heat can be stored very easily and in an environmentally friendly manner in large heat storage tanks—unlike complicated battery storage systems. This energy storage system has been tried and tested for many decades. Currently, many PV systems in private households and other buildings are facing the decision of what to do with the electricity generated by the PV system once the EEG feed-in tariff expires. Many of the systems installed in private households still work perfectly, so dismantling them does not make sense. ratiotherm offers intelligent solutions for dealing with such surplus renewable electricity efficiently and intelligently.

The advantages of power-to-heat at a glance:

The solution for the post-EEG era
By using the Max-Heater, a large portion of the electricity generated can be used after the feed-in tariff expires without having to feed it into the grid at uncertain conditions. This allows you to make your own energy transition.
Robust and simple technology
The conversion technology has been tried and tested over many years and is extremely robust. The p2h heating element technology converts electricity into heat at a ratio of almost 1:1 (1 kW of electricity becomes 1 kW of heat).
Environmentally friendly storage
By converting electricity into heat, storage in water is very simple and efficient. Furthermore, no CO2 is produced.
Easy retrofitting
PV systems can be retrofitted with power-to-heat relatively easily, thereby replacing fossil fuels efficiently and cost-effectively. During the summer months in particular, such a system can heat up to 100% of the drinking water required.

See for yourself:

Our proven products in this sector

Max-Heater F12

Using electricity directly via a heating rod

PVT Collector

New generation of solar collectors

The possible variants of Power-2-Heat in single-family homes:

P2H originally comes from larger plant engineering and is now widely used in the bioenergy sector (biogas, wind), partly in the field of control energy. Energy suppliers use such systems to stabilize the power grids at times of oversupply. In private households and smaller commercial buildings, two types of Power 2 Heat applications are particularly prevalent:

Power-to-heat with heating element:

The simplest way to use surplus electricity from photovoltaics to heat your own building is with a heating element. Most systems are installed in existing buffer storage tanks as a screw-in solution and, depending on the technology, they operate in cycles or, in some cases, in a modulating manner.

The major disadvantage here is that the heat is introduced into the lower part of the heat storage tank. This causes the contents of the tank to mix, which reduces the amount of heat available to the consumer. This is because the colder layers further down in the buffer tank are heated by the heating element due to the difference in density of water at different temperatures (see also the operating principle of Oskar° stratified storage tanks).

Based on our experience with stratified storage technology, we have given this topic a great deal of thought and are therefore offering our Smart Energy PV as the optimal solution for the p2h photovoltaic market. This system operates externally—i.e., not built into the storage tank—and therefore has no problems with storage tank mixing. The user has immediate access to heat at a defined temperature level.

Power-to-Heat Smart Energy von ratiotherm

Power-to-heat with heat pump:

A very efficient way of using Power-2-Heat in single-family homes is to combine PV electricity with a heat pump.

It does not matter whether it is an air source heat pump or a ground source heat pump. However, the heat pump must have the appropriate contacts or signal inputs and the associated control system to communicate with the inverter, smart meter, or energy management system. Heat pump systems with speed control, known as inverters, are particularly suitable. This technology allows the system to operate at reduced power (i.e., reduced speed) even when solar radiation is not so intense, thus enabling the maximum amount of PV electricity to be used in the heat pump.

ratiotherm offers only heat pumps that can communicate with PV systems, and all heat pumps are equipped with inverter technology as standard. Our WP Max-Air air source heat pump can even provide active cooling during the summer months using PV power if required.

The operating principle of the Max Heater as a Power-2-Heat system for photovoltaics

Max Heater is designed as a wall-mounted device, similar to a PV inverter. It is connected to an existing buffer tank or an Oskar° stratified storage tank via a pump group. The speed of this pump group is varied by the integrated control of the Power-to-Heat system depending on the available excess current from the PV system. This ensures that the system only uses actual excess current. As soon as the washing machine starts, for example, Max Heater reduces its output or the speed of the pump. The p2h system receives information on the current excess current in real time via a smart meter or an energy management system, as is widely used in the PV industry (a 0-10V or BUS signal is sufficient). The user can set a target flow temperature for the Max Heater, which results in the storage of immediately usable heat in the buffer storage tank.

Direct comparison of Max Heater with conventional heating elements

Hardly any other device on the market covers such a wide range (0.1–15 kW) with full modulation in a single unit as the Max Heater heating device. The necessary certifications for power grid compatibility and hydraulic protection of the heating circuit are available. Full modulation is an important component for maximizing the device’s own power consumption. Compared to conventional on/off solutions or multi-stage solutions, the ratiotherm Power-to-Heat solution generates significantly more from excess power, as the excess power is dissipated more precisely than in multi-stage operation.

Possible uses and areas of application for the p2h Max Heater device

Variations in use:

Excess electricity as own consumption for hot water production
Use of surplus electricity from inverters capped by the energy supply company to optimize the 70% rule.
Combination of battery storage and Max Heater
Connection of additional consumers via radio-based applications possible
Can also be used as a sole heat generator, for example in vacation homes or other buildings that are only used occasionally.
Further variations are possible at any time by our programmers by adjusting Max Heater according to customer specifications.

Areas of application

In private households, for heating drinking water in summer and, in some cases, for supplementary heating in winter.
In the field of agriculture, for the provision of process heat (cleaning milking systems, etc.), but also for heating support, because there are many very large PV systems here that also supply usable amounts of electricity in winter or in bad weather.
In the commercial sector, p2h can easily cover the often low demand for drinking water, especially since large roof areas (halls, etc.) are often covered with PV systems and the necessary power is available.
Alternative Nahwärmenetze, sogenannte Kalte Nahwärmenetze können zur Unterstützung der vorhandenen Energieerzeuger mit Power-2-Heat Systemen auf Basis von Wärmepumpen oder Elektroheizstäben ausgestattet werden

Power to Heat mit Max Heater by ratiotherm

Our fully-fledged Max Heater heating device can use excess current from photovoltaic systems or other sources in a fully modulating manner from 0.1 to 15 kW, thereby increasing the self-consumption rate of your PV system.

Erfahren Sie mehr!

FAQ: Questions and answers on the topic of power-to-heat

Is power-to-heat worthwhile for private households?

Yes. Power to Heat is worthwhile for private households. Power to Heat is particularly interesting for households that are no longer eligible for the EEG feed-in tariff. Otherwise, there is no longer any profit to be made, either in terms of energy or costs. The investment costs remain manageable even when combined with heating systems based on heating oil or gas. The technical effort is also straightforward, as are the investment costs. Power to Heat can be combined with any type of heating system.

What exactly is the EEG feed-in tariff?

EEG is the abbreviation for the Renewable Energy Sources Act (Erneuerbare-Energien-Gesetz). Consumers who generate electricity from photovoltaics and feed it into the public power grid receive a feed-in tariff under the EEG. The EEG was an incentive for private and commercial customers to install photovoltaic systems in their homes. At the beginning of the 2000s, the feed-in tariffs were, of course, considerably higher than they are today. Now, after around 20 years, consumers with photovoltaic systems are wondering what will happen when the EEG expires. This is where Power to Heat comes in. Use your own electricity to generate heat. Save oil, gas, and wood.

Is it complicated to install Power to Heat technology?

As a general rule, the more modern your existing system is, the easier it is to install Power to Heat technology. On the electricity side, Power to Heat requires three components: Electric heating
• Pump
• Control system for communication with the existing feed-in meter (for use of self-generated electricity)

Today, there are significantly more intelligent measuring systems than in the past, and many of the values required for operating the P2H system are already integrated. Installation is somewhat more complex in older PV systems, where additional measuring systems are required. Hydraulically, i.e. on the water side, the P2H system must be connected to the buffer storage tank. Here, too, modern systems are easier to combine. Ultimately, however, any connection is possible, albeit with a little more effort in older systems.

Why is Power to Heat an environmentally friendly storage method?

Power to Heat is an environmentally friendly storage method because it uses a thermal battery. Our Oskar° stratified storage tank converts solar energy and can store it for long periods of time. The environmentally friendly aspect lies primarily in the simple transfer of energy. Heat is a luxury commodity. Power to Heat technology saves solar energy that would otherwise be lost by converting it into heat, thus generating an attractive new source of energy. You can use surplus energy from summer days at a later time. The more energy is generated and stored, the longer it can be used at a later date. Private households are faced with a decision: battery or Power to Heat. Batteries are often the more expensive option. Power to Heat means using inexpensive storage. In addition, Power to Heat technology with buffer storage can store energy, whereas a battery cannot.

Is Power to Heat with a heating element or a heat pump the better option?

In Verbindung mit Power to Heat ist die Wärmpumpe das effizientere Medium als der Heizstab. Sie verwandelt den gleichen Anteil an Strom in mehr thermische Energie als ein Heizstab. Während die Umwandlung beim Heizstab bei 1:1 liegt, schafft die Wärmepumpe beispielsweise 10 Kilowattstunden Strom in 30-40 Kilowattstunden thermische Energie umzuwandeln, also das 3-4 Fache. Allerdings ist der Heizstab in der Anschaffung deutlich günstiger als eine Wärmepumpe. Er wird oft als Aufrüstung verwendet. Eine Wärmepumpe ist vorzugweise bei einem generellen Energie-Wechsel von alten auf erneuerbare Energien sinnvoll.