More than 2,000 houseboats are moored in Amsterdam's canal system, the so-called canals, and have both water and electricity connections. But now they have been upgraded. In a kind of »Houseboats 2.0«, Amsterdam has created a new settlement: it consists of 30 floating houses, most of which are self-sufficient in regenerative energy via a sophisticated system. For cloudy days, the grid operator has had a single, shared narrow grid connection laid all the way to the neighbourhood.
Energy Management System for Energy Communities
The power supply is made possible by the energy management system developed by the Fraunhofer Institute for Industrial Mathematics ITWM and other partners in the ERA-Net-Smart Grids Plus project »Grid-Friends«. »We have developed our existing energy management system for individual houses into an energy management system for entire energy communities,« explains project leader Matthias Klein. »The system controls photovoltaic systems as well as heat pumps, fills the battery storage tanks, ensures that the batteries in the electric cars are charged, and thus also supports sector coupling«. This is no easy task, because even on dark days there must always be enough energy available for everyone without overloading the shared grid connection.
The energy management system has a modular structure and serves as a kind of »hub for energy«: At any given time, it analyses where the energy is needed and where it is not. Here, the photovoltaic systems, heat pumps and energy storage units installed in the houses in the Amsterdam neighbourhood function like a single large system. For example, when the residents of house A are on holiday and the residents of house B are having a party and currently have an increased electricity requirement, the energy from the photovoltaic system flows from house A to house B, among other places. As soon as it is dark outside and the system does not generate any electricity, the system instead accesses the energy storage units – and this also across the houses.
Smart Control of the Energy Stores
The management system gives each module its very own intelligence, which enables smart control of the energy storage units – for example, the photovoltaic systems can be operated at full load. Actually, by law photovoltaic systems are not allowed to feed their maximum output into the grid, but must be regulated when the sun is strong - otherwise the grid would be overloaded. So it is precisely when the sun comes crashing down from the sky and the modules could generate a lot of electricity that they have to be throttled. With the help of the energy management system, this is not necessary: the portion of the electricity that the grid operators do not take off flows into the storage tanks and can be used later.
In addition, a forecasting model improves the efficiency of electricity storage. It uses the weather forecast to predict how much energy can be expected from the photovoltaic systems in the coming hours and how much heat will be consumed, and controls the storage based on the results. If, for example, the sun still shines in the morning, the systems do not run at full load. If, on the other hand, it should clear up in the afternoon so that the systems would have to be throttled down, the energy management system postpones energy storage until the afternoon instead. This means that the storage units are not charged with the first kilowatt hour produced – as would normally be the case – but only in the afternoon. The storage units are still full until the evening. No energy is lost.
Charging the Electric Cars
Residents' electric cars must also be supplied with energy – preferably at times when the photovoltaic systems are producing sufficient power. Nevertheless, nobody wants to stand in front of a car with a flat battery. »Residents can use an app to specify with a click what minimum charge level they currently want for their car,« says Klein. For a trip to the supermarket, for example, the user selects 50 percent and connects his car. The system then recharges the battery to the desired level – if necessary, even with power from the grid. If the sun shines, it continues charging beyond this value. However, if there is a power shortage, the system postpones further charging until later. This has two advantages: On the one hand, the self-sufficiency of energy increases, and on the other hand, charging above the necessary level does not affect the network operator – the energy network is greatly relieved.
Not only interesting for Large Settlements
The modules can also be used individually and tailored to the desired application. »There are already 60 to 70 permanent installations of our system – from individual private households to canteens and entire companies to a sewage treatment plant. While the system in Amsterdam shifts power peaks of up to 250 KW, in industry it has so far controlled 150 KW,« explains Klein. Since the beginning of 2019, the system has been marketed by Wendeware AG, a spin-off of the Fraunhofer ITWM.