El método de análisis de costos del ciclo de vida es el método más comúnmente aceptado para evaluar los beneficios económicos de los proyectos de conservación de energía durante su vida. Por lo general, el método se utiliza para evaluar al menos dos alternativas de un proyecto determinado (por ejemplo, evaluar dos alternativas para la instalación de un nuevo sistema HVAC: un sistema VAV o un sistema de bomba de calor para condicionar el edificio). Solo se seleccionará una alternativa para la implementación basada en el análisis económico.
The basic procedure of the LCC method is relatively simple because it seeks to determine the relative cost-effectiveness of the various alternatives. For each alternative including the base case, the total cost is computed over the project lifetime. The cost is commonly determined using one of two approaches: the present worth or the annualized cost estimate. Then, the alternative with the lowest total cost (or LCC) is typically selected.
Using the cash flow diagram of Figure above, the LCC amount for each alternative can be computed by projecting all the costs (including costs of acquisition, installation, maintenance, and operating the energy systems related to the energy-conservation project) on either:
- Un único importe de valor presente que se puede calcular de la siguiente manera:
Este es el enfoque más comúnmente utilizado para calcular el LCC en proyectos de modernización energética.
- Múltiples costos anualizados durante la vida útil del proyecto:
Tenga en cuenta que los dos enfoques para calcular los valores LCC son equivalentes.
En la mayoría de los proyectos de eficiencia energética, el flujo de caja anual sigue siendo el mismo después de la inversión inicial.
En este caso, el LCC se puede estimar con base en el costo inicial IC y el costo anual AC de la siguiente manera:
Ejemplo
A building owner has $10,000 available and has has three options to invest his money as briefly described below:
- Replace the entire older boiler (including burner) with more efficient heating system. The old boiler/burner system has an efficiency of only 60 percent whereas a new boiler/burner system has an efficiency of 85 percent. The cost of this replacement is $10,000.
- Replace only the burner of the old boiler. This action can increase the efficiency of the boiler/burner system to 66 percent. The cost of the burner replacement is $2,000.
- No hacer nada y no sustituir ni la caldera ni el quemador.
Determine the best economical option for the building owner. Assume that the lifetime of the retrofit project is ten years and the discount rate is 5 percent. The boiler consumes 5,000 gallons per year at a cost of $1.20 per gallon. An annual maintenance fee of $150 is required for the boiler (independently of its age). Use the life-cycle cost analysis method to determine the best option.
Solución
The total cost of operating the boiler/burner system is considered for the three options. In this analysis, the salvage value of the boiler or burner is neglected. Therefore, the only annual cash flows (A) after the initial investment on a new boiler are the maintenance fee and the net savings due to higher boiler efficiency. To present the calculations for LCC analysis, it is recommended to present the results in a tabular format and proceed as shown below:
Por lo tanto, el costo del ciclo de vida de la opción A es el más bajo. Por lo tanto, se recomienda que el propietario del edificio reemplace todo el sistema de caldera/quemador.
This conclusion is different from that obtained by using the simple payback analysis [indeed, the payback period for option A, relative to the base case C, is SPB(A) = ($10,000)/($1,765) = 5.66 years; and for option B, SPB(B) = ($2,000)/ ($546) = 3.66 years].
Note that if the discount rate were d = 10 percent (which is unusually high for most markets), the USPW would be equal to USPW = 6.145 and the life-cycle cost for each option will be
Por lo tanto, la opción B se convertirá en la más eficaz económicamente y será la opción recomendada para el propietario del edificio.
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