Example_HP

S2 examples for heat pumps

This page serves as a guide for implementing a RM for a heat pump. It provides some example S2 messages for same (fictional) heat pumps.

How is a heat pump flexible?

A heat pump is a device that uses electricity to heat a building and/or Domestic Hot Water (DHW). A heat pump can do this efficiently by utilizing a heat source (typically the air or ground). In this guide we'll make the distinction between an all electric heat pump (which provides the heat for a building on its own) and a hybrid heat pump (which is typically a smaller heat pump which uses a natural gas boiler for peak demands). When a heat pump provides DHW, it typically uses a buffer tank to store an amount of hot water.

There are in principle three ways a heat pump can be energy flexible. Depending on the set-up, these forms of energy flexibility can be combined.

1. Using the Domestic Hot Water (DHW) buffer as a source of energy flexibility
   Allow some variation in the water temperature, or don't heat the buffer immediately after DHW consumption. This requires a bit larger DHW buffer than strictly necessary, or a reliable forecast of when what amount of DHW is required.
2. Using the thermal mass of the building as a source for energy flexibility
   Reduce or stop heating the building for a certain period, without significantly affecting the room temperature. Preheating (again, without significantly affecting the room temperature) could even prolong the period in which the heat pump can turn off or reduce its power. This is typically implemented by defining a small temperature bandwidth (e.g. half a degree Celsius) around the thermostat set point.
3. (Hybrid heat pump only) Switching between electricity and natural gas
   A hybrid heat pump can temporary reduce or stop its electricity consumption by starting or increasing the power of the natural gas boiler. This way, the heat output of the hybrid heat pump isn't significantly affected.

Choosing the right Control Type

When implementing S2, it's important to choose the right Control Type(s) to implement in the RM of the heat pump. S2 is a language for conveying energy flexibility to the CEM without making any assumptions on what the CEM is optimizing for. Although there typically are multiple Control Types that can be used for a heat pump, it is preferred to pick the one that conveys the most information and control options to the CEM, so the CEM can do the best optimization that adds the most value.

As a general rule, when there is some form of energy (in this case heat) buffering involved, Fill Rate Base Control (FRBC) is the best Control Type. When there is no flexibility involved, but there is an option to switch between different fuels (as is the case with the hybrid heat pump), Demand Driven Based Control (DDBC) typically is the best option. Both Control Types give the CEM relatively direct control over the heat pump.

However, in S2 it is up to the RM to implement whatever Control Type it seems best, or it can even implement multiple Control Types. There are two alternatives that still allow the CEM to utilize the energy flexibility of the heat pump, but give less direct control over the heat pump. The risk of these control types is that CEM might utilize the energy flexibility less effective or that it makes the energy flexibility of the heat pump not usable for certain use cases, decreasing the value of the energy flexibility.

The first alternative Control Type is Power Envelope Based Control (PEBC). With PEBC, the CEM cannot control the heat pump, but it can request it to limit its energy consumption for certain moments. The Resource Manager defines how the CEM is allowed to limit the consumption. It is preferred (but not mandatory) that the RM provides a forecast of the energy consumption.

The second alternative Control Type is Power Profile Based Control (PPBC). Here the RM could offer the CEM some alternative power profiles for the near future to choose from. It could, for example, offer a power profile where it starts heating DHW right away, and an alternative one where it does it later. It is for this Control Type necessary that the RM can make forecasts for the near future.

The possible Control Types to implement are summarized in the table below.

DHW buffer	Thermal mass building	Switching between natural gas and electricity (hybrid heat pump only)	Preferred Control Type	Alternative Control Type
No	No	No	n/a	n/a
Yes	No	No	FRBC	PEBC or PPBC
No	Yes	No	FRBC	PEBC or PPBC
No	No	Yes	DDBC	PEBC or PPBC
Yes	Yes	No	FRBC	PEBC or PPBC
No	Yes	Yes	FRBC	PEBC or PPBC
Yes	No	Yes	FRBC	PEBC or PPBC
Yes	Yes	Yes	FRBC	PEBC or PPBC

Example: All electric heat pump utilizing the DHW buffer using FRBC

TODO

Example: Hybrid heat pump without buffering using DDBC

TODO