Hybrid boiler rooms to reduce the carbon footprint of buildings

Can you tell us more about this project, and in particular what makes it so innovative?

The Hybrid Boiler Room project, now marketed as SCHOC (Solutions Calibrées Hybrides à Objectif de déCarbonation) by ENGIE Solutions in France, is a hybrid solution for our customers with boiler rooms that are currently mainly fuelled by gas.

We were looking at ways of decarbonising our customers’ heat production, particularly for the renovation of collective, residential and small tertiary buildings without having to completely change existing, in-operation boiler rooms, which supply buildings of all ages and types, some equipped with radiators, others with underfloor heating and others with convection heaters. We’re talking here about power ratings of between 50 and 500 kilowatts.

That’s how the idea of hybridisation came about, by keeping the existing heating system, a gas boiler for example, provided it is still functional and efficient. In these conditions it would be counterproductive to destroy it and put something else in its place. We prefer to add a low-carbon heat source, either an air/water heat pump, a containerised biomass boiler, using wood chips or pellets, or a water/water heat pump using surface geothermal energy and BHEs. 

Is it this hybridisation that makes it innovative? 

What’s innovative about this approach is that you don’t have to change everything and replace it from scratch. 

The challenge for our R&D department was being able to combine an existing boiler of one make with equipment of another make and another technology in a simple and standard way, and to get them to work together properly. Heat pumps and boilers work in different ways. For example, the performance of an air-to-water heat pump will depend very much on the outside temperature.

So we had to put in place control principles with 2 heat producers available on the market, and get them to work together to ensure the customer’s comfort, without affecting their heating or the production of their domestic hot water.

We worked on the design, the hydraulic diagrams and the regulation of this hybrid boiler room so that it could be quickly adapted to any type of building, asking ourselves all kinds of questions, for example: 

- What design is required to match the existing boiler? 

- What size should be chosen to ensure a satisfactory percentage of coverage by the low-carbon solution without oversizing this new low-carbon producer? 

Can you give us an example of these sizing choices? 

For example, in the west of France, for an apartment block with a hybrid boiler room, a heat pump can be installed with a capacity corresponding to 27% of the total capacity required when it is 0 °C outside (ensuring a temperature of 55 °C). This power ensures that 65 to 70% of the heat will be produced in a low-carbon way. And we save gas for peak demand and times of extreme cold. This will make it possible to supply customers with heat from several sources, with greater flexibility and less fluctuation in energy prices.

Didn’t these hybrid boiler rooms exist before you started working on them?

We are leading the way in this solution. This is because we offer heat ‘as a service’. We install and operate the heating system and ensure customer satisfaction and comfort. 

As well as the pilot installed on our premises, the first installation has been operational since the beginning of the year in a residence in Brittany, equipped with an air/water heat pump alongside a gas boiler, which is exactly what you would expect from a hybrid heating system.

We’re in the middle of a roll-out phase, with 9 more hybrid boiler rooms scheduled to be installed over the summer, and around forty sales offers currently being finalised.

How are you going to show all this off at Vivatech? You can’t bring a mini heating system with you!

We are in the process of producing a LEGO® model of a small building equipped with a boiler room, with different emitters on each floor: underfloor heating and radiators. The model includes the heat pump in hybrid with the boiler, along with the electricity meter, the gas meter and the controller.

This model, which measures around 64 cm x 64 cm x 70 cm, will give you a concrete idea of the solution, and we’ll also have a screen on which we’ll play a video explaining how it all works.

What do you expect from Viva Technology?

First of all, we want to give a meaningful illustration of ENGIE’s position on the alliance between electrons and molecules. We’re firmly convinced that this is the direction we need to take, and we’re going to put our money where our mouth is! Today, the project is no longer in the pilot phase. It has been transformed into a commercial offering that sales representatives and engineers are proposing all over France. 

We are also going to take advantage of this visibility to inform potential customers that ENGIE can support them in their efforts to decarbonise collective, small tertiary or residential buildings. 

This exhibition of a finished product also demonstrates the innovative capacity of ENGIE’s Research and Innovation department.

So, to sum up, our objective is visibility and commercial development.

What’s your next challenge?

Our next challenge is to adapt our existing monitoring tools to enable real-time monitoring of new installations throughout France. In September, we’ll have 10 projects up and running, but we’re hoping for around a hundred next year, and then more after that. We will need digital resources to monitor all these systems and ensure that they are working properly and performing well.

Another challenge will be to offer a wide range of refrigerants for heat pumps. We currently use R32, a transition fluid, and are in the process of integrating new suppliers with natural refrigerants for the heat pump.

Because that will soon be something you have to do, right?

Yes. We know that at some point we will no longer be allowed to use refrigerants with a high global warming potential. For the time being, this is still possible, but we chose transition fluids (R32) from the outset, because of our commitment to climate issues. We wanted to be ahead of the game and start integrating natural fluids, such as R290 (propane), which is a natural refrigerant.

What question would you have liked me to ask you?

The question “How do you know it works?”

And the answer is that we know it works, because for the last 2 years we have had this system ourselves at Cylergie, and it heats our research lab (workspace, offices and showers, etc.).

So you’ve been able to test that it works!

Exactly, it works. We’ve been able to gather data on this use and assess how much carbon this solution has saved. 

And we will also be presenting this information - operating principles, orders of magnitude for coverage rates and energy savings - at the show.

Visit the ENGIE stand (J39) at Porte de Versailles in Paris from 11 to 14 June to discover the innovative solutions that make ENGIE the leader in energy transition.