Matching the heat supply to the demand can be quite a challenge for district energy operators. A peak in the demand can be balanced by an increased heat production, and this often leads to the use of fossil fuel boilers. On the other hand, when the heat supply exceeds the demand, the result is often that the excess heat goes to waste. Ideally, the excess heat should be saved for when there is, once again, a rise in the demand.
To ease this distribution challenge, thermal energy storage (TES) can help to balance the demand and supply during peak hours and high seasons, as well as improve capacity & maximise system efficiency. The key is finding the right storage solution according to the network and the need.
During this webinar examples of both short term storage are included, with the example of Rotterdam’s Heat Hub, and seasonal storage with the lessons learned from the conversion of an old oil tank into seasonal storage in the PITAGORA’s project. The vision and perspectives of Göteborg Energi for seasonal storage presented, with a final session for an interactive discussion with the audience.
1. Warmtebedreijf Rotterdam and the Heat Hub
The construction phase of the Heat Hub and the buffer tank of the Warmtebedreijf Rotterdam (Dutch for Heat Company Rotterdam) is presented. The aim of Warmtebedreijf Rotterdam is to be able to use waste heat from the large industrial area of Rotterdam.
A central part is the Heat Hub; the goal of which is to attain less use of fossil fuels, reductions of local emissions, and cost efficiency. Since pipelines of 500 mm diameter are needed to go right through the city, stakeholder engagement is necessary. In order to achieve that, an open source tool is used with a design contest. One part was the heat buffer (heat storage), called “The Pie of Rotterdam”. This is a beautiful design, which was actually shortlisted for the design award in Rotterdam in 2014. The heat hub provides considerable primary energy and CO2 savings.
2. PITAGORAS – Transforming an oil tank into seasonal thermal storage
The objective of the EU project PITAGORAS was to demonstrate a highly replicable, cost-effective and high-energy efficiency, large-scale energy generation system. This would allow sustainable urban planning of very low energy city districts. One part of the PITAGORAS project was to transform an oil tank into seasonal thermal storage, which is described in detail. The heat for this should be supplied from a large solar thermal plant, and from industry waste heat. The heat would then be used in a nearby city. However, the demonstration failed for economic reasons, mainly because of the fall of the oil and gas price. The general barriers for this type of project, and how they can be overcome, are described. Although this demo failed, the PITAGORAS project actually became a door opener for a big solar project in Graz.
3. Seasonal storage visions and possibilities
An overview of Thermal Energy Storage (TES) is provided. The reasons to use TES are presented, as well as possible heat sources. Also, the main TES technologies are described with advantages and disadvantages: ATES (Aquifer TES), BTES (Borehole TES), CTES (Cave TES), PTES (Pit TES), “Skanska TES” (CTES+BTES). The investment costs of TES storages are also discussed, using data from installations already done. Generally, they may be profitable – especially if they are large enough. Finally, the evolution of district heating, past, present and future, is shown.
4. Questions from the audience
- Have you had any response from the oil industry? [On the PITAGORA’s presentation]
- Can cold be stored in the same way as heat can?
- Please comment on the issues of price, profitablility, replicability, and dissemination regarding storage.
- Why are there not so many projects that use TES, despite its profitability?
- What are the conditions needed in order to be able to implement the use of the storages that we have heard about today? What do you already need to have, can anyone try it, or does it only work in certain contexts and situations?
Date of webinar