Production of DECS DECH DECH DECED CARBON WATER Production of DECS low carbon DECS DECH

Paralain Bodin, manager of the Consulting Office and Jean-Pierre Hue, consultant

Global warming and energy precariousness require new heat production systems capable of producing more than they consume at a controlled and environmentally friendly cost.A real technological breakthrough!

Preamble: the production of domestic hot water has become preponderant

The climatic urgency and the outbreak of the cost of energies have become priorities which impose shares without delay.These are the new challenges of the next decades to limit the multiplication of natural disasters and preserve populations.

We are talking about carbon neutrality!

In the construction sector, all buildings are affected both new constructions and rehabilitation.The energy renovation of buildings affects all activities, residential, tertiary and industry.If there are several levers of action to reduce heating consumption by acting on thermal insulation of buildings and heating systems, many progress remains to be made.Furthermore, it is clear that many buildings cannot be isolated from the outside and call for new solutions (Haussmannian buildings, with exposed or millstone bricks, case of facades in models).

Beyond heating consumption, the production of domestic hot water has become preponderant in the recent buildings of the residential or accommodation.Once the disputed distribution networks and the installation of solar panels are difficult to further reduce the consumption of this position to warm sanitary water.

In the context, this article presents a new duplicable hybrid system capable of converging decrease in consumption, respect for the environment and reduction in collective buildings.

Presentation: of a hybrid dick production system

2-1 - General

This hybrid system is designed to meet the heating and domestic hot water needs of buildings displaying consumption greater than 250 MWh/year, the equivalent of 50 dwellings for annual domestic hot water needs and 30 dwellings with productionof heating.

This is a patented solution recorded at the INPI under n ° 15 53643, resulting from the clever combination of one or more gas cogenerations coupled with Air-Eau Thermodynamic units.

This combination uses two technologies known to professionals who have largely proven themselves and which makes it possible to have a Gazelectricity Energy Mix.

So far heat pumps and cogenerations were used separately while in this case, heat pump and cogeneration are complementary and operate simultaneously or alternately.

The heat pump ensures preheating of domestic hot water and cogeneration ensures thermal supplement.

The electrical energy produced by cogeneration is used to supply the heat pump.

In order to avoid short cycles and respect a minimum operating time of one hour between each start -up cycle, the system has two storage reserves with a substantially equivalent capacity, one dedicated to the preheating of the water by theheat pump, the other dedicated to cogeneration.

Preheating and extra temperatures are 40 ° C and 75 ° C respectively to more or less 5 ° C depending on the fields of application.

For production of domestic hot water, the water temperature is warmed from 40 to 60 ° C via an extra exchanger supplied from the primary cogeneration balloon.

To illustrate this combination, below the principle scheme.

Figure 1: Operating principle of the DHW hybrid production system

In this example, thermal and electric yields of gas cogeneration are 63% and 33% respectively and the performance coefficient of the heat pump is 4 (extract air recovery).

The combined system then gives us for 1 MWh consumed a thermal production of 1.95 MWh calculated as follows:

Thanks to this high performance of almost 200%, we get:

2-2- Operating methods

Different operating modes are available, namely simultaneous operation as presented above, operation with stopped cogeneration and heat pump in service or cogeneration in service with the heat pump stopped.

"Simultaneous" operation

It is this operating mode which gives the highest yield system, 160 % for the lowest external temperatures, 190 % for external temperatures of around 7 to 8 ° C and 230 % for external temperaturesgreater than 15 ° C (PCI data).

Operation "Cogeneration at the stop and heat pump in service"

This operating mode makes it possible to maintain continuity of service when maintenance interventions are necessary on cogeneration.In this case, the set point of the heat pump is offset from 40 to 55 ° C.

In half-season, where we observe external temperatures of the order of 10 ° C, it may be interesting to relieve cogeneration in favor of the heat pump to extend the number of hours between two revisions while benefiting froma cost of supply of competitive energy.

If the decarbonation of buildings is a priority, this operating mode is to be favored for external temperatures above 12 ° C.Indeed, in France, electrical energy is not very carbonated and consumption is lower during this period.In summer, where electrical energy is abundant, there are opportunities to increase pricing attractiveness for an erasure in winter thanks to cogeneration.

"Cogeneration in service and heat pump" operation "

This operating mode makes it possible to maintain continuity of service when maintenance interventions are necessary on the heat pump.It is also a way to relieve the heat pump when it is strongly requested during negative external temperatures where frequent defrosting cycles are observed.In this operating mode, the electrical energy produced by cogeneration is debited on a thermoponator placed in the primary capacity.The performances obtained are equivalent to those of a high -performance energy gas boiler.This operating mode is also a means of erasure on the public electricity network during point calls and allows, in compensation to benefit from better tariff conditions for the purchase of electricity.

2-3 - Focus on system management

Heat pumps and cogenerations are controlled by their own communicating automaton and allow their manufacturers to visualize the proper functioning as well as remote remote tellings if necessary.The hybrid system is equipped with a preprogrammed supervision automaton allowing the visualization of the whole performance.Users can access certain password settings and specialized technicians can access all setting and registration data using a manufacturer code or by connecting a special USB stick.

As mentioned in § 2.2, the above -mentioned operating modes can be programmed according to different criteria to the choice of the user, in particular:

The supervision automaton is connected to independent automata through a bus to allow centralized communication from a single point.

The supervision and piloting system includes a cabinet with protections, Trend type IQVIEW 8 display and TREND IQ4/96/XNC/BAC/230 controller, etc..

The supervision automaton is configured to pilot or reassemble the following data:

Operating prerequisites

Operating principle in "normal" mode

The operating principle is backed by a balance of electrical consumption of the heat pump and the electrical production of cogeneration.

Power modulation is ensured by a measurement center equipped with voltage and intensity sensors placed on the power supply of the heat pump and its auxiliaries.An analog signal 4-20 mA or 0-10V is then transmitted to the cogeneration module to adjust electricity production to the consumption of compressors.

The micro-cogeneration load pump works in variable flow to maintain a constant starting temperature of the order of 80 ° C (if the return temperature is low, the flow rate decreases and if the return temperature is high, theflow rate increases).It is the co -manatee automaton that pilots this pump.

Degraded modes

Anomaly on the cogeneration module all defect on the cogeneration module leads to its stop and returns an alarm to the supervision center to alert the manufacturer and the operator.The production of hot water is then ensured by the heat pump on the intervention of the operator in charge of shifting the set point from 40 to 55 ° C.If this set temperature is insufficient, thermoplongers can be used in addition.

Anomaly on the pacen case of anomaly on one of the compressors of the heat pump, the supervision automaton starts the start of the next compressor and sends an alert to the manufacturer and the operator.Hot water production is then ensured by cogeneration and compressors of the CAP still available.If the power is insufficient, the thermoplongers provide the.

Total anomaly on the CAP and cogeneration in total breakdown of the heat pump and cogeneration, the continuity of service is ensured by the preheating and additional thermoplongers.They are powered by the public electricity network.

Results guarantee

Like all innovative systems, it is recommended to entrust the installer with driving and maintenance to obtain the expected results.This increases the involvement of the work market holder and avoid the usual remarks "It is the operator who did not understand how it works!"Or vice versa," the installer did anything!»».

This is the option chosen for the first installations made where the market holder engaged in a performance which consisted in contracting the amount of heat necessary to reheat 1 m3 of domestic hot water from 10 to 60 ° C.This warranty fixed at 7 years allowed the installer to familiarize himself with the system and to train its technicians with the technology of thermal engines and heat pumps.If the first two years of commissioning generally call for settings, the guarantee of result is very incentive to correct the "small faults" of youth.It should be recognized that a combined system of this nature, apparently simple on paper calls for a certain vigilance about automatisms.There is no room for improvisation at the risk of obtaining poor results and abandoning the project.

It is clear that the results of the first installations were very encouraging despite some imperfections in the programming of automation which required some corrections.

On the other hand, it was essential to simplify the task of the installers, in particular in the dimensioning of the installation and its realization.It is in terms of connections and the choice of equipment that improvements have been made.

As such, the use of "plug and play" technology today facilitates the task of installers and the collaboration of an industrial group has made it possible to remedy certain incompatibilities, in particular communication protocols between regulation materials, beachespower and modulation, prerequisites before tests and settings and feedback on the supervision automaton or directly from the industrialist.

From theory to practice

Figure 2: Return of experience on a residence of 46 dwellings classified E

The advice, technical study office specialized in CVC intervened as a prime contractor, on behalf of a social landlord and proposed this hybrid solution.It is a residence of 46 dwellings classified E which was selected.It is a building with a useful surface of 3604 m² of 7 floors on ground floor and basement, built in 1989 (Figure 2).At the origin of building the building, the heating of the accommodation was provided by electric convectors of the "toaster" type.Domestic hot water was produced by individual electric water heaters in the bathrooms.Actorate electric heater with a capacity of 16 liters were placed under the sinks.The ventilation of housing was ensured by a single mechanical ventilation system, self -relieved flow, made up of air inlet mouths in the main parts and extraction mouths in sanitary facilities and kitchens.

The cost of heating and hot water loads amounted to more than € 1250, value 2016, or almost € 20/m² shab.

The work program aimed at improving the comfort of occupants, decreases in significant charges and a reduction in consumption by at least 40% to get out of the list of the most energy -consuming buildings.

We observe in the photo of Figure 2 above, apparent brick facades prohibiting the implementation of thermal insulation from the outside.

After feasibility study, the advice proposed the following work bouquet:

Figure 3: cramming of the hybrid module

To increase the performance of the hybrid system and guarantee the expected load reductions, heat pumps capture the fatal energy contained in the air extracted from the VMC.Initially, the VMC of this residence rejected outside 2900 m3/h of air at 20 ° C, or almost 50 MWh per year or 15% of heating and DHW consumptions.This recovered energy makes it possible to boost the performance coefficient (COP) of the heat pump in favor of a drop in consumption and avoids defrosting cycles during very low external temperatures.

The new hybrid system consists of a CAP comprising two compressors with a total thermal power of 28 kW and a preheating balloon with a capacity of 2000 liters.It covers 65% of DHW needs at a 40 ° C preheating temperature.The electrical consumption of the CAP is 100% covered by a gas cogeneration of a nominal power of 7.1 kwe and a thermal power of 15.3 kW (Figure 4).

The CAP starts on the public network, before cogeneration, and the two compressors of the heat pump operate in cascade, each ensuring 50% of the thermal load.

Figure 4: Mini-cogeneration

When the thermal load increases, the second compressor starts and vice versa when the load decreases.The supervision automaton permanently measures the absorbed intensity of the heat pump and sends a signal of 4 to 20 mA proportional to the thermal load of the installation to obtain a balance between consumption and electricity production.After starting the CAP, cogeneration starts at 50% of its charge.At this stage, the PLC measures absorbed electrical consumption and sends a progressive power rise to balance between consumption and electricity production.As indicated in § 2.3, the minimum operating duration of cogeneration is 1 hour.In descendant load, the compressors gradually stop one after the other, until total stop.When the CAP is stopped the cogeneration stops if the temperature of the primary balloon in the lower part is greater than or equal to 55 ° C.Otherwise, it continues to operate by debit the electrical energy on the thermo diver until reaching this temperature.It is therefore up to the designer to pay particular attention to the dimensioning of preheating and extra capacities because otherwise, operating durations cannot be respected and expected yields are not reached.

On this residence, the new DHW production is positioned in terrace roof in a prefabricated room.A collective distribution network in "umbrella" was created to join the former departures of the individual balloons deposited.The columns descend in each of the housing stacks in order to reduce the course of the pipes between vertical distribution and drawing points.

The horizontal terrace distribution is calorified by rock wool shells with water -repellent protection dressed in isoxal sheet.

The new DHW distribution network is maintained at a minimum temperature of 50 ° C by a closure network until the DRC.This is equipped in the upper part of each column with a balancing valve for adjusting hydraulic curling flows.Protection against the risks of legionnels is ensured by a permanent circulation of 1,200 l/h for the entire residence, or just over 25L/h per accommodation and 300 l/h per column.This peculiarity makes it possible to have a minimum traffic speed in the network and to maintain the DECS in permanent motion to avoid all stagnations of water on the peripheral layer of the tube.

As with all renewable energy facilities, help is highly recommended to guarantee continuity of service in the case of a major disfunction.On this residence, continuity of service is ensured by electric thermoplongers placed in preheating and extra capacities.

However, it is necessary to be vigilant as to the prolonged use of these service continuity devices which can quickly generate significant additional consumption costs.

To avoid these drifts, a guarantee of result as indicated in paragraph 3 has been implemented.It avoids resorting too frequently to service continuity devices and encourages maintenance staff to follow their facilities closely.

As part of the result warranty objectives, the performance of the installation is drawn daily using the supervision automaton and the dedicated platform.

Key figures

Advances since 2019

After being noticed and awarded the various calls for projects, below:

The concept has taken a new step to evolve towards a semi-industrial manufacturing in favor of a reduction in production costs while respecting quality standards.COLLARD TROLART, specialist in French thermal equipment, installed in Meaux is one of the first partners to have made one of the first prefabricated couplings from industrial manufacturing (Figure 5).

Beyond the manufacturing processes, and at the request of several designers specializing in CVC, title V system has been deposited to take into account system performance.This request has given rise to a modeling of calculations with regard to Th-C-E rules.This title V system was obtained by decree of June 8, 2021 and concerns thermal regulations of existing buildings.

Figure 5: AMHYBRID® generator

Towards collective heating applications!

The ECS combination is changing today towards collective heating applications.

Unlike domestic hot water production applications, the "heating" solution has two cogenerations and two heat pumps, each equipped with two "on-off" refrigeration compressors

This configuration makes it possible to give the coupling, four stages of power to meet the amplitude of thermal load of a heating season.

For heating applications with domestic hot water, preheating is ensured by two capacities instead of a single.One is dedicated to DHW while the other is dedicated to heating as illustrated in the diagram below (Figure 6).

Figure 6: Heating and DHW production diagram

In this configuration where the thermal powers are more substantial, the heat pumps are placed outside, on a terrace, in a courtyard or any other widely ventilated spaces.The concept can advantageously complete an existing boiler room to introduce renewable energies, reduce carbon emissions and energy consumption.In the context of energy optimization, it may be relevant to use the existing boiler room for negative external temperatures and reduce defrosting cycles.It is also a way to ensure continuity of service during maintenance operations on heat pumps or cogenerations.Regarding the energy efficiency of the coupling in "heating" application, we must expect a little lower yields than in DHW.This explained by lower external temperatures than in summer.

Identically, DEC production, the Télé-suivi platform is being finalized to offer all the data necessary for meticulous monitoring of installation performance.This monitoring tool has become a must to engage in energy performance contracts and guarantee objectives in consistency with the new challenges of the energy transition and carbon neutrality.

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