HPS inaugurates home with solar hydrogen storage system

In Schöneiche, a suburb east of Berlin, the first self-sufficient hydrogen house is starting practical testing. A solar year-round storage tank should cover the demand for the modern timber house. The goal of the FlexEhome research project is to show how a home can be self-sufficient with electricity and heat if it is suitably well insulated. In the scope of this project, the participants are also testing grid-serving services.

The photovoltaic system of the brand new single-family home in the street Schillerstraße was deliberately designed to be very large with a total output of almost 30 kilowatts – so it can generate a solar energy surplus for the production of clean hydrogen. Currently, most buildings with photovoltaic systems and batteries produce too much electricity in the summer, however, not enough in the winter months. So far, there is no seasonal storage.

In a practical test, the FlexEhome research project will now demonstrate that it can be done differently: Electricity should only be released into the grid or taken out when it is also useful for the grid. This is possible due to a significantly larger storage capacity compared to batteries and the production of hydrogen, which can be stored for longer periods of time. Thanks to this flexibility, grid stability is improved and the need for expansion of the decentralised distribution grids is minimised. In this way, the residents of such a building contribute to power grid stability and supply security.

“In the future, such decentralised flexibilities will be indispensable for the success of the energy transition,” emphasised Zeyad Abul-Ella, head and founder of Home Power Solutions (HPS), at the ceremonial presentation of this solar hydrogen house. An essential component of the project is the long-term storage picea from HPS, which stores the surplus electricity from the solar system in the summer in the form of hydrogen by means of electrolysis. In winter, the green gas is converted back into electricity and heat via the fuel cell.

AEM electrolyser from Enapter

The hydrogen is produced by an AEM electrolyser 2.0 from the German-Italian manufacturer Enapter. The module can start and ramp up relatively quickly. The battery storage is a German-made lead-gel accumulator with a net capacity of 20 kWh. Lead – although a toxic heavy metal – has the advantage that there is already a well-established recycling system – especially for starter batteries from motor vehicles.

Civil engineer Abul-Ella developed the complete system of electrolyser, fuel cell, hydrogen tank as well as lead storage and ventilation unit himself almost ten years ago. However, the picea system is not cheap, costing 120,000 Euro for the full system. Nevertheless, sales of the so-called all-season power storage units have increased strongly in recent months. More than a hundred units are already in operation, and more than 500 have been ordered.

The Berlin-based company can hardly keep up with the orders. The waiting time is currently about twelve months. The production of HPS is therefore to be expanded further. Also because of projects such as FlexEhome: Participating partners are, for example, the heat pump manufacturer Vaillant, the timber house builder Albert Haus and the Technical University of Berlin.

Solar facing to the east-west and south

In order to smooth out the solar harvest from the roof already during production, the majority of the photovoltaic modules with 27.4 kilowatts were installed as a roof-integrated solution facing east-west. In addition, seven modules with a total of 2.4 kilowatts are located on the balcony railing facing to the south. Both together reduce the PV midday peak by 30 percent (see Fig. 2) – and therefore extend the runtime of the electrolyser by four hours per day in summer. “This increases the hydrogen yield by as much as 40 percent,” says Daniel Wolf from HPS. The engineer is the network coordinator of this innovative project.

The electrolyser with a total of four bundles of pressurised gas cylinders, each with an electrical output of 300 kWh (see Fig. 3), is located in a timber house on the north side of the detached house to store the H₂ gas from the summer months for the winter months. According to the calculations of Daniel Wolf, the hydrogen storage tank would be completely full again by July. The space heating demand of the almost 150-square-metre home is around 40 percent below that of a KfW55 house. This high insulation standard is also necessary so that the house can supply itself with electricity and heat all year round. This is the key and the basis for full green supply.

But the long-term storage of electricity should also pay off economically in the future – through trading on the electricity market. Because there are very high exchange electricity prices every now and then, as on some days in December 2022, when it was the equivalent of 60 ct/kWh. On the other hand, there is the extreme of negative electricity prices, such as at the beginning of June 2021, when minus 5 ct/kWh was requested. This is where the H₂ storage of HPS, which has reserves at all times, could pay off, says Daniel Wolf.

The (TU) Technical University of Berlin monitors all energy flows

The hydrogen is turned back into electricity and heat in a combined heat and power generation plant, where waste heat is also used. In combination with a heat pump, this ensures a year-round supply of the house with self-generated solar power. The interaction with the heat pump in particular will be investigated in greater detail through this project in the coming months.

Soon, a family of four will be living in the project house for rent. They will pay a lower rent compared to the local area, but will have to allow professional visitors and technicians access to the technical room from time to time by appointment. In order to document the full supply and a grid-serving feed-in, over the next few months the TU Berlin will also monitor all energy flows in the house in detail.

The researchers will continue to support the project until at least the end of 2024. In addition to the energy balances, they also look at the CO₂ emissions. “In the end, we want to assess whether a building like this is worthwhile for climate protection,” says Alexander Studniorz from the TU Berlin. The scientists are conducting a life cycle analysis for this purpose. The scientist’s assumption is that it is the temporal shift in electricity consumption that will have a positive impact on the CO₂ balance. This is because, unlike in homes with a PV system and a battery storage system, no additional grey electricity needs to be drawn from the grid on a cold winter night when many fossil-fuel power plants are in operation. “The seasonal buffer in particular, in combination with the heat pump, therefore guarantees low CO₂ emissions all year round,” predicts the TU researcher.

Author: Niels Hendrik Petersen