1.1 Background of the study
Solar photovoltaic/thermal solar collector (PV/T) is a collector that combines solar thermal collector and photovoltaic cells in one single hybrid generating unit. It generates both thermal and electrical energy simultaneously. The excess heat that is generated in the PV cells is removed and converted into useful thermal energy. Therefore, PVT modules generate more solar energy per unit surface area than a combination of separate photovoltaic panels and solar thermal collectors.
In recent years, photovoltaic electricity is increasingly being looked upon as the quintessentially “green” energy option for the future, entailing virtually no emissions during its use phase, and larger and larger energy returns on investment[2, 3]. However, it still suffers from some non-negligible limits[3, 4].
A wide research have been carried out by many researchers on the design optimization of this hybrid collector in search of efficient and inexpensive design suitable for mass production for different practical application. Florscheutz suggested an extension of the Hottel-Whillier model for the analysis of PV/T system. Raghuramman presented numerical method predicting the performance of liquid and air PV/T flat plate collectors. Cox & Raghuramman, performed computer simulations on air type hybrid system. Bhargava et al and Prakash reported the effect of the air mass flow rate, air channel depth, length and fraction of absorber plate area covered by solar cells (packing factor). Garg et al presented the first simulation study of the single-pass photovoltaic/thermal air heater with plane reflector. Garg & Adhikari reported the performance analysis of a hybrid photovoltaic/thermal collector with integrated CPC toughs.
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Aspect and cost analysis results for standard PV modules and PV/T systems give an idea for the practical use of the photovoltaic[7, 12]. The considerations of the environmental impact of the PV modules by using the Life Cycle Analysis (LCA) methodology have been presented for the typical photovoltaic system[13-15]. In addition the comparison of the PV/T systems over standard PV and thermal system confirmed the environmental advantage of the PV/T system[16, 17].
1.2 Problem Statement
Currently, there is no optimum design to determine the energy (electricity) that can be produce by the PV/T system. As known, the costs to of the system are quite expensive and most consumers are reluctant to install purchase and install the PV/T solar collector at their premises.
1.3 Research Objective
To determine the cost benefit ratio by the evaluation of the Annual Energy Gain (AEG) and the Annual Cost (AC) of the PV/T system performance. By the evaluation of the AEG and AC, we can now calculate the energy produce by the PV/T system and compared it with the annual cost of the PV/T solar collector.
1.4 Significance Of The Study
From the study of the LCA on the PV/T system can determine the optimum design for the research model.
2.0 LITERETURE REVIEW
2.1 Life Cycle Assessment
A systematic set of procedures for compiling and examining the inputs and outputs of materials and energy and the associated environmental impacts directly attributable to the functioning of a product or service system throughout its life cycle.
-ISO 14040.2 Draft: Life Cycle Assessment - Principles and Guidelines
What is LCA?
Life Cycle Assessment (LCA) is a technique for assessing the potential environmental aspects and potential aspects associated with a product (or service), by:
* compiling an inventory of relevant inputs and outputs,
* evaluating the potential environmental impacts associated with those inputs and outputs,
* interpreting the results of the inventory and impact phases in relation to the objectives of the study.
- ISO 14040.2 Draft: Life Cycle Assessment - Principles and Guidelines
2.2 LCA For PV/T Solar Collectors
LCA for the PV/T solar collector were evaluate by the performance and the cost factor of the collector which lead to annual energy gain (AEG) and annual cost (AC) of the system[18, 19].
2.2.1 Performance Of The Collector
The performance of the collector was evaluated by obtaining the electrical and thermal efficiency. The combined photovoltaic-thermal efficiency of the system is the sum of photovoltaic and thermal efficiencies of the system[20, 21].
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Marked to Standard
PE = Electrical power generated by the photovoltaic cells
m = Mass of flow rate
S = Incident solar radiation on the collector surface
T0&Ti = The fluid inlet and outlet tempeture
CR = Concentration ratio
Cf = Specific heat capacity of the flowing fluid
Ac = Collector aperture area
2.2.2 Annual Energy Gain (AEG)
Annual thermal energy gain (ATEG) and the annual electrical energy gain (AEEG) per unit collector area can be expressed as follows:
ATEG = m Cf (T0-Ti)top
AEEG = ηpvtS(P)(Ac)top
P = Packing factor
Top = The operational time
And therefore the equation for the annual energy gain can be expressed as:
AEG = ATEG + AEEG
2.2.3 Annual Cost (AC)
To determine the annual cost, several cost factors need to be calculated. This included the annual collector cost (ACC), the annual maintenance cost (AMC), the annual pumping cost (APC) and the annual salvage value (ASV) where annual cost can be define as,
AC = ACC + AMC + APC - ASV
The annual collector cost is defined as,
ACC = CRF x CI
Where capital recovery factor (CRF) and capital investment (CI) is given by,
CRF = i(i + l)ⁿ/[ (i + l)ⁿ - 1]
CI = CAC + CSSC + FC
i = interest rate
n = collector life time
CAC = cost of collector array including the photovoltaic panel cost
CSSC = collector support structure cost
FC = fabrication cost
The annual maintenance cost (AMC) of the collectors is considered to be 10% of the annual collector cost (ACC)
The annual pumping cost (APC) is given as,
APC = (m ∆P/ρ)topCE
CE = cost of the electricity
∆P = the pressure drop across each flow channel
The annual salvage value (ASV) is given as:
ASV = SFF x SV
Where the salvage value factor (SFF) and salvage value (SV) is given by:
SFF = i/ [ (i + l)ⁿ-1]
SV = 0.1 CI
From the all the equation studied, the evaluation of the AEG and AC will be calculate to find the cost benefit ratio the PV/T solar collector.