A double for the future

Combination of fossil and renewable heating technology ▪ The goals are clear: a building stock that is as climate-neutral as possible by 2050 at the latest and a significant reduction in CO2 emissions from buildings by 2030. It is far less clear how this can be mastered in the individual case – whether existing building or new construction – with the lowest possible costs, taking into account all of the challenges of additions and additions. Hybrid heating systems are a viable solution that can also be used to react flexibly to future changes. But they offer many more advantages. → Martin Bauer

It wasn’t just in the European elections that the countless media reports on the subject of climate protection left a clear mark: as early as February 2019, in a YouGov survey commissioned by the German Solar Industry Association, two-thirds of Germans were in favor of at least a proportion of the new heating system being fed by renewable energies when modernizing the heating system – provided that this is technically reasonable.

However, investors and modernizers have to weigh many aspects in order to find future-proof, project-specific advantageous and practicable solutions, which

Hybrid heating systems meet these conditions because they combine two independent heat generators with different benefits and energy sources. Most commonly, they consist of a gas or oil condensing boiler, as well as a renewable energy-based system. As a suitable partner, in addition to a solar thermal system, an air-to-water heat pump is increasingly recommended.

In hybrid systems, home stations can meet the high requirements in new buildings economically and without compromise.

The fresh water module of the stratified storage tank BSP-W is designed for relatively low temperatures and, in combination with a heat pump, ensures hygienic and energetically optimized heating of drinking water in a continuous flow system.

Advantages and future options

A condensing heat pump hybrid is suitable for use in both new and existing buildings. Depending on the building and the type of application, such a heating system offers fundamental advantages:

It is also advantageous that hybrid heating systems can be optimally used in conjunction with a project-specific, individual buffer and hot water storage concept.

Here is an example: In new multi-family housing, larger buffer storage solutions are often used to optimize heat pump run times. Here, for example, the Wolf stratified storage tank BSP-W is particularly suitable for use with a heat pump. This is because the attached fresh water module ensures both hygienic and energetically optimized DHW heating in the flow, as it is designed for relatively low temperatures.

The bivalence point plays an essential role in the operation of a condensing heat pump hybrid system.

Alternative, parallel and partially parallel

With a condensing heat pump hybrid, there are three typical types of bivalent operation in terms of heat provision: alternative, parallel and partially parallel. The bivalence point (BP) and the switch-off point (AP), two fixed or (partially) variable outside air temperature values, which are designed specifically for the project, play an important role:

The system controller can determine the cut-off and bivalence point according to different criteria (command variables), which can be fixed or variable. Typical examples of fixed reference variables are: Heat source, flow/return and outdoor temperature, as well as any blocking periods of the energy supplier for heat pump electricity tariffs. Variable criteria can be, for example: photovoltaic power surpluses, CO2 emissions and different energy tariffs.

Which operating mode is ultimately used depends on the specific project. For example, in bivalent alternative operation, the condensing boiler can operate at higher flow temperatures if the existing radiators in an (unrenovated) old building require higher flow temperatures on very cold days.

In order to illustrate the interrelationships more clearly, two market segments that are particularly attractive for condensing heat pump hybrid systems – both from the point of view of specialist tradesmen and planners and from the investor’s point of view – are examined in greater detail below. Homeowners: the new construction of multi-family houses and the (partial) renovation in the owner-occupied sector.

Example project of a hybrid system in a new multi-family building with eight residential units.

Hybrid systems in apartment buildings

Especially in metropolitan areas, living space is to be created quickly for private buyers for their own use and also for renting (as a capital investment). Due to limited building space, high land prices and the lowest possible construction costs, small and medium-sized multi-family houses (MFH) with up to 16 residential units are very much in vogue.

But under these conditions, how can a heating system be constructed that is as cost-effective and reliable as possible, that facilitates compliance with the EnEV, and that also fulfills the EEWarmeG obligation to use renewable energies (the previous draft of the GEG provides for similar requirements)??

The use of brine/water and water/water heat pumps is recommended by the builder (developer, general contractor, etc.).) is usually ruled out due to the high investment costs. However, even air-to-water heat pumps with large heating capacities quickly reach their limits: because of the initial costs, their size and noise emissions in small properties.

In new MFH construction (without local and district heating connection compulsions), the criteria of operational availability and reliability also play an important role in system planning. This is another reason why the use of gas condensing technology (natural and liquid gas) in combination with an air-to-water heat pump is a good choice here. This results in the following main advantages:

The EEWarmeG regulations could of course also be met with gas condensing technology and solar thermal energy. However, this usually fails due to the higher costs – although the coverage share (from renewable energies) for heat supply (without domestic hot water heating) in combination with environmental heat only has to be at least 50%. In a bivalent parallel operation mode, this target can be achieved more easily, because the heat pump runs as long as possible.

Here is an example: Assuming a heat pump coverage of 61 % at a bivalence point of 5 °C, the power share is only 19 %. In contrast, the heat pump in bivalent alternative operation must already have a power share of 35 % in order to achieve a coverage share of at least 50 %. If the heat pump is to be subsidized via the market incentive program (Bafa), a bivalence point of 2 °C (or lower) is required. In this case, the power share of the heat pump in bivalent parallel operation would be at least 31 %.

Example project for a hybrid system as part of the renovation of a single-family house built in 1980.

Hybrid systems in the home

In single- and two-family homes, a condensing heat pump hybrid is particularly interesting if a heating system modernization is imminent and the homeowner

As a rule, both heat generators have similarly high heating capacities. The heat pump takes over the base load all year round, while the fossil condensing boiler comes into operation (briefly) during peak loads and when there is a high demand for hot water. With similarly sized heat generators, it is possible, for example, with the manufacturer Wolf, to store intelligent operating modes in the BM-2 operating module:

In combination with the EEBus interface and other additional components, the BM-2 control module enables the intelligent use of self-produced photovoltaic power for heat pump operation. This noticeably increases the degree of self-sufficiency, which more and more homeowners are specifically aiming for.

The situation is somewhat different if the home is to be comprehensively renovated for energy efficiency and the radiators are to be replaced by panel heating. Then mostly the monovalent or. mono-energetic use of a heat pump system should be more economical – provided that the hot water demand is generally not too high.

If the energy-related renovation measures are carried out in stages over a longer period of time, the existing heating system can be supplemented with a heat pump right from the start. The heat pump is then designed in such a way that it alone can cover the planned lower heating load and the existing old boiler can be decommissioned (after completion of the refurbishment).

When designing a heating system for new and renovated low-energy buildings, it should always be taken into account that controlled ventilation with heat recovery may be useful or even necessary – to protect the building fabric and the health of the occupants as well as for a comfortable climate all year round. This additionally reduces primary energy consumption and CO2 emissions – especially if PV surpluses are used for operation.

Like this post? Please share to your friends:
Leave a Reply

;-) :| :x :twisted: :smile: :shock: :sad: :roll: :razz: :oops: :o :mrgreen: :lol: :idea: :grin: :evil: :cry: :cool: :arrow: :???: :?: :!: