Reformers project takes a step toward practical heat storage
From the very beginning of the Reformers project in Plan Oost, one central question guided the work: how can residents make the smartest possible use of their own sustainable energy? Heat storage played an important role in that search. Initially, the team considered a battery based on PCM (Phase Change Materials). Although promising on paper, the system proved difficult to use as a primary source for the heat pump. Storage temperatures were too low, and the amount of heat that could be stored was insufficient.
During the project, the team therefore looked for an alternative that would be robust, affordable, and practical for existing homes. That search—alongside continued exploration of PCM for higher temperatures—led to the NEStore heat battery: a compact storage system that operates at higher temperatures and is specifically designed to deliver hot water at times when there is no sunlight. For the Van Dijk family, who actively participate in the Reformers project, this system promised to be an interesting match for their home and energy profile.
Why the NEStore Heat Battery is a better fit
The NEStore stores heat up to 110 °C, making it more efficient than the earlier PCM setup. The battery supplies hot tap water only, which allows it to operate at higher temperatures without complex integration with the home’s heating system. Installation is relatively simple: a water connection, a power connection, and a floor that can support the weight. That last point is important, because heat batteries—especially PCM-based ones—are heavy. Installers note that moving such heavy systems up narrow Dutch staircases is often difficult or even impossible. The NEStore is filled with water only after installation, which helps.
For the Van Dijk family, the NEStore offered what they needed: a way to reduce their dependency on gas, by using their own solar power and using it to produce and store for hot tap water to use during evening and early morning hours.
We have already written about Plan Oost, you can read about the kick-off here.
What does it offer residents?
The NEStore is particularly attractive for households with solar panels. The system converts solar electricity into hot water that remains available for days. As a result, the share of self‑consumed solar energy increases—a financial advantage now that the net‑metering scheme is being phased out. Producing hot water with own electricity to replace gas is better than feeding electricity back to the grid at low rates.
Comfort is another benefit: hot water is always available, even after several cloudy days. Thanks to strong vacuum insulation, stored heat is retained almost completely.
Another advantage is durability. The NEStore contains no moving parts and no chemical storage materials that degrade over time. The battery lasts more than thirty years and requires virtually no maintenance.
The remaining issue is the relatively high cost of the equipment. We are in discussion with Nestore to lower the purchase price. At the current price level of the NEStore and relatively low prices for gas, the payback period is still very long.
Looking ahead
Although the NEStore is an interesting solution for daily heat storage, one question remains: how can we store heat for longer periods, such as from summer to winter? The current technology is mainly suited to bridging day‑night differences and perhaps a few additional days. Seasonal storage requires different systems.
Menno van Dijk is keen to explore the next step: heat storage that can bridge not just days but the entire season, and—just as originally planned—serve as a source for the heat pump that will be installed later. Reformers Heiloo Plan Oost is happy to support this effort. Because we already have a participant group working on home battery systems, we can closely follow the progress of this research during our meetings. Updates will also be shared on the Duurzaam Heiloo and Reformers website so that everyone can stay informed in both English and Dutch.
Other channels
Stay updated on the latest trends in renewable energy innovation with REFORMERS, by following:
Our last Newsletter