Category Functional Design of the mCCHP-RES System

Circuit of hot/cold water distribution to the residence (CH5/CH6)

The CH5 circuit has the role of distributing hot water to the residence (for heating during winter), while the CH6 circuit—that of distributing cold water to the residence (for cooling during summer). Commutation from hot/cold water supply is through three-way control valve driven by electric motor. The thermal load of the circuits is represented by a system of ventilo-convectors and heaters placed inside the heated spaces. The source of heat or cold may be the hot water tank or the cold water tank. The thermal agent is nonharsh, treated water, which is circulated in the hydraulic circuit by a pump. This pump is placed on the return of the thermal agent which comes from the ventilo-convectors or radiators...

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Thermal Subsystem Components

First, the ST panel and back-up boiler must be dimensioned. After that, the hydraulics and the pumps will be dimensioned. The third source is the Stirling engine which was dimensioned in electrical subsystem. The Stirling engine has an internal cooling system with a pump and expansion vessel, and a plate heat exchanger. The second circuit which makes connection between the plate heat exchanger and the storage tank (outer system) must be dimensioned. The flow rate in the outer system (aided by the pump which runs continuously when the CHP is operating) is 1-2 m3/h, resulting in a spread of 20-10 °K at maximum load. Finally, will be dimensioned the heat storage tank and the expansion tank. All hydraulic circuits must be protected at over temperature and pressure.

A. Solar thermal panel

The ...

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Sizing of the System Components

The system components sizing consist in establishing the nominal values for the required characteristics of each component, the choice of those products which meets these characteristics of the component, and the evaluation of the daily operation time, toper, for each supplier, and the daily use time, tuse, for each con­sumer, taking into account:

• the monthly quantities of energy resulting from any kind of evaluation, whether it refers to consumption or load, and whether it refers to the main components or to the complementary, and

• the nominal technical characteristics of the components available in the market.

8.1.1 Electric Subsystem Components

In the house the electric installations have installed power Pn = 12 kW...

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Building the Functional Schemes

Nicolae Badea

For the structural model with thermally activated chiller was adopted, at the global level, the functional scheme presented in Fig. 1 in Chap. “Functional Design of the mCCHP-RES System”.

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Performance Evaluation at the Couple Building-System Level

The energy performance of a building shall be expressed in a transparent manner and shall include an energy performance indicator and a numeric indicator of primary energy use based on primary energy factors per energy carrier. The new numeric indicators of primary energy use refer to specific value for on-site pro­duction and the share of renewable energy.

Taking into account the data given in the Table 40 in Chap. “Structural Design of the mCCHP-RES System” and Table 12 in this chapter, and applying the rela­tions from 69 to 71 in Chap. “Structural Design of the mCCHP-RES System” for the couple building-system, were obtained the values for the integrated energy performance Ep. tot = 217.48 kWh/m2 year and the share of renewable RER = 25. 61 % (Table 15).

Table 15 Integrated ...

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Performance Improving

Improving the performance indicators of the system is achieved by analyzing the specific energy production system components and through actions to reduce losses but especially by diminishing the excess energy produced. The off-grid system

Fig. 11 Balance of electrical energy production and consumption

supplies the thermal and electrical energy for residential consumption only. During operation, the whole CCHP system control is based on balancing the electrical energy production and consumption. Control of this balance consists in appropriate modulation of the electrical energy obtained from CHP unit, so that, together with the current PV panel production, to cover the electrical energy current demands...

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Evaluation and Improving of the Performance

Nicolae Badea

5.1 Performance Indicators at the System Level

The first indicator is Percentage of Energy Saving or Primary Energy Save (PES) that refers basically to the percentage of fuel saved from the energy production of the CCHP system compared to the same energy produced by the reference system.

Table 13 Fuel consumption and performance indicators


System load

PV and ST panels load






esys (kWh/ m2)

#sys (kWh/ m2)

ePV (kWh/ m2)

qTP (kWh/ m2)









































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Load Sharing

The system load should be split between suppliers, to thus find the load for each supplier. This problem is called load sharing and the solution of the problem depends on the system structure. Using data from Table 11 for monthly energy specific consumption of the mCCHP system in the case of cooling with TCC and from Table 6 for monthly specific power and heat production of the panels and building, we can determine the load sharing of the CHP unit and back-up boiler. To determine the energy produced by the cogeneration unit and back-up boiler were used the Eqs. 5961 in Chap. “Structural Design of the mCCHP-RES System”. The load sharing of the mCCHP system with TCC is shown in Table 12.

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