The challenges of operating a heat transport network

‘We are starting off with two users, Eneco and Vattenfall,’ Jasper explains. ‘It should be emphasised that these energy companies do not order heat from WTS: they specify what they want to transport, and that’s what WTS provides: heat transport. WarmtelinQ does this by pumping a specific amount of water through a closed-loop (pipeline) system that transports hot water (100-120°C) from the source to the customer and cooled water (50-70°C) back from the customer to the source. The energy companies have now signed contracts on their own with suppliers (heat sources), such as port industries and thermal waste processors. These energy companies will inform WarmtelinQ where the heat will be coming from. In the case of Eneco, a heat transfer station is being built in Vlaardingen, which will serve as the entry point for the heat. Where the heat source is often a factory or waste incineration plant, for example, that’s not the case here. The heat will come from Eneco’s own “Leiding over Noord” (LoN) heat grid, which collects the heat from the waste incineration plant in Rozenburg. This heat will then be transferred from the LoN grid to WarmtelinQ at the Kethelplein station and WTS will transport it from there to The Hague.’

‘Eneco places an order for the transport of a specified volume of heat; this is called a nomination. They take into account the heat that will be lost along the way. WTS supplies them with the relevant data for this. So, the heat Eneco wants to arrive in The Hague, plus the heat loss, is what they need to nominate for the entry point. Each day, WTS receives a nomination for each hour of the following 24 hours. We use these nominations to create a heat transport plan.’

‘In the first phase, WTS will only serve Eneco, who will in turn serve homes and businesses in The Hague. Once the pipeline has been extended to Leiden and everything is ready, we will also supply Vattenfall with heat. For this purpose, an entry point is being built in the Vondelingenplaat industrial area at the Port of Rotterdam.’

‘Currently, each of these energy companies has a contract with a single heat supplier (heat source), but it is expected that energy companies will eventually connect multiple heat sources. It will then be up to the energy companies to determine how much heat they will procure from one source and how much from the other. WTS will then need to know which source the heat will come from. We’ve opted to align our process to that future situation right now already. Accordingly, Eneco will, from the outset, also submit a nomination for the entry point in Vlaardingen, even if they are the only heat source to start out with.’

‘Eneco and Vattenfall are required to report the expected temperature of the water at the entry point as well as the expected temperature of the water as it returns from The Hague and Leiden, after the heat has been transferred to the local district heating network. We need to know how much the water will have cooled. Equipped with that information we can then calculate the entire heat transport plan. So, every day we receive 24 sets of data corresponding to the following 24 hours.’

‘The data on the temperature at the entry point and the return temperature after the heat has been transferred to the local district heating network may not vary significantly. After all, we will not be able to make significant changes within an hour. With this quality standard, we aim to increase the predictability of the system. WarmtelinQ is being built to provide a certain base load, so we don’t expect much variation in the various values per hour. We have also made contractual agreements about how much the water may increase or decrease in temperature compared to the previous hour. This applies both to the capacity (measured in megawatts) and the temperatures, both of which must fall within a certain range.’

‘With the addition of Vattenfall as a second user in the system in phase 2, we will be able to even more precisely detail the extent to which our users can follow the established heat transport plan. We do not want to see a situation where deviations caused by one user affect the operations of the other.’

‘And in terms of megawatts, we cannot supply 80 megawatts one hour and 40 the next: the supply will gradually increase and gradually decrease. Still, as you can imagine, the demand for heat and hot water increases significantly when everyone gets up in the morning and decreases again in the evening after everyone’s gone to bed. That’s where the energy companies’ control system comes into play. They have peak and backup facilities, such as a buffer they can charge overnight using the base load WarmtelinQ provides, since this is not in use at night. In the morning, they can use this buffer to handle peak demand while WarmtelinQ continues to supply the base load. While WarmtelinQ can easily balance a portion of the day-night fluctuations in a heat network, it cannot handle all of it on its own; the energy company needs to manage the remaining portion.’

‘Once we have multiple users active in the system in the second phase, the energy companies will be required to follow the set heat transfer plan very precisely. Nonetheless, there’s sure to be temperature and pressure deviations in the system at any given time. This could be due to the sum of several small measurement and control deviations, user misjudgements, or outages affecting the WTS or user installations. WTS uses a buffer tank to correct these disruptions. We refer to these disruptions as “imbalances”, and the way we correct them is called “balancing”. We will balance the system using an enormous buffer tank we are building in the Vondelingenplaat industrial area. This is how we will fulfil our responsibility and ensure a stable heat supply.’

‘Perhaps I should explain more about the buffer. This is where a major difference between gas and water comes into play. Gas can be compressed. When faced with fluctuations in the gas network, the pressure in the network will increase or decrease somewhat. As long as this remains within a given range, this will not affect anyone. You can actually see the entire Dutch gas network as a kind of buffer. This isn't the case with water, however, because water cannot be compressed. That’s why every heating system that uses water has an expansion tank. Water flows in or out of this tank when the pressure changes. Our system also has this: that’s the buffer tank we’re building. Water flows in and out of this tank whenever the average temperature of the water in the system changes. This happens continuously. Water will automatically flow in or out of this buffer tank without us being able to, or wanting to control this. This buffer tank also supplies additional water through the supply or return pipeline when the system faces deviations we want to correct (balance).’

‘Another consequence of having multiple customers is that we have to make sure that the costs are shared, like the electricity costs for the pumps in Delft, for example. However, how do we know who has used what? We have to allocate the costs correctly. The same applies to the costs of balancing the grid, that’s to say charging and discharging the buffer tank. The water in the buffer tank is heated and that heat comes from Eneco or Vattenfall. But who gets what share? We calculate this based on measurements at their entry and exit points. This way, we arrive at a certain balance, and we settle that balance between the parties. This is called the allocation process.’