Category Green Energy and Technology

Evaluation at the Couple Building-System Level

The energy performance of a building [22] 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, which may be based on national or regional annual weighted averages or a specific value for on-site production.

The energy performance indicator is energy class of the building, which by Energy Performance Certificates (EPCs) give information only on building prop­erties, resulting in energy needs (used).

For the mCCHP system, the energy efficiency indicator indicate conversion efficiency on the system and the PES indicator indicate the percentage of fuel saved from the energy production of the CCHP system compared to the same energy produced by the reference ...

Read More

Performance Evaluation of the Potential Structural Models

7.4.1 Evaluation at the System Level

In the fourth step of the design process have been identified the potential structural models by customizing the general structural model. Table 7 shows the set of identified potential structural models. Now the performance of these models should be evaluated in order to retain the best. The structural models can be obtained from the particularization of the cooling system (with mechanical compression or with thermal compression) and of the auxiliary sources (with thermo solar panels or with photovoltaic panels). With all the structural models, the electric load control is achieved by adjusting the fuel consumption of the Stirling engine, and the thermal load control—by controlling the fuel consumption of the additional boiler...

Read More

Structural Model Type on-Grid with Thermal Compression Chiller

The governing strategy of the CHP unit is changed ensuring at any moment the thermal energy needed. In this case the prosumers can export electricity to the grid. The solar panels are dimensioned in this case to produce maximum energy in the month with the greatest consumption and radiation available, similar off-grid (resulting к;т = 0.062 where July is the month with the greatest radiation poten­tial). If the prosumers focuses on the electricity export to the grid, the dimensioning of the PV surface is done according to the conditions set about architectural sus­tainability and utilization factors determining the surface of the PV panels using the relation:

krPV = 0.4 – krST (68)

The results of numerical simulation for the illustrative exercise are shown in Table 38 and graphical dis...

Read More

Structural Model Type off-Grid with Thermal Compression Chiller

The off-grid system ensures the energy only for own residential consumption in the two main forms, electrical and thermal. The CHP unit is governed by the power
drive strategy ensuring the balance between PV production and electricity con­sumption of the residence. The thermal energy balance is kept in equilibrium by the additional boiler that balances the ST production, the CHP unit production and the specific thermal energy consumption of residence.

In order to increase the performance indicators of the CCHP system, especially its efficiency, the PV electricity production is correlated to the energy consumption eliminating the excess production for the month with the biggest PV production and electricity consumption, respectively (in this month ePV = esys)...

Read More

Performance Evaluation and Improving in the Case of Structural Models with Thermal Compression Chiller

Procedure for determining the performance indicators is similar to that described in Sect. 7.2. Admitting the same values for the overall efficiency of CHP unit and of additional boiler as in Sect. 7.2, and using data from Table 32 for monthly energy specific consumption of the mCCHP system in the case of cooling with thermal compression chillers, and from Table 6 for monthly specific power and heat pro­duction of the panels and building, we can determine the energy production of the CHP and backup boiler. The results of the energy production of the mCCHP system with thermal compression chiller are shown in the Table 36.

The power and heat production represented in the graphic (Figs. 39 and 40), depending on the number of functioning hours of the system in a year, allows the analysis of e...

Read More

Structural Model Type on-Grid with Mechanical Compression Chiller

Unlike the case of the off-grid model, when the imposed condition is the balance between required and produced power and heat, in case of the on-grid system the

e_load l=l e_sys ———— Poly. (e_load) ——— Poly. (e_sys)

image117

Fig. 33 Electricity balances

 

Structural Model Type on-Grid with Mechanical Compression Chiller

Month

 

Fig. 34 Heat balances

image119

 

Structural Model Type on-Grid with Mechanical Compression Chiller

imposed condition is the balance between required and produced heat only while the power can be produced in excess.

To exemplify, two alternatives could be considered. In the first alternative, the load sharing strategy could consist in adjusting the nominal area of the PV and ST panels (which are the key variables of the strategy) so that in months with high solar radiation, the power load to be fully covered by PV panels...

Read More

Structural Model Type off-Grid with Mechanical Compression Chiller

The off-grid system supplies the thermal and electrical energy for own 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.

But, by producing electricity, the CHP unit produces thermal energy in mean time. The amount of this energy cannot be modulated because it is proportional with the amount of electricity produced.

This is why the thermal energy balance is reached by using an additional boiler which, together with the thermal panel and CHP unit, supplies the thermal energy...

Read More

Performance Evaluation and Improving in the Case of Structural Models with Mechanical Compression Chiller

To calculate the two indicators PES and EFF, we need to determine the specific fuel consumption of CCHP system. Specific fuel consumption is the sum of fuel input for cogeneration unit and additional boiler. Its determination involves knowledge of cogeneration unit and boiler energy production, and cogeneration unit and boiler efficiency.

To exemplify, let us consider the illustrative exercise from the paragraphs above. Using data corresponding to the illustrative exercise, namely from Table 31 for monthly energy specific consumption of the mCCHP system in the case of cooling with mechanical compression chillers, and from Table 6 for monthly specific power and heat production of the panels, we can determine the energy production of the CHP and backup boiler...

Read More