Technical and Economic Evaluation of Ground Source Heat Pump

Ground source heat pump is a use of underground shallow geothermal resources for heating, cooling new air conditioners. Because of its relatively high heat source temperature, stable throughout the year, does not change with the ambient temperature changes, so whether it is winter heating, or summer cooling, ground source heat pump COP are much higher than other heat source heat pump. At present, ground source heat pump has been widely used in many countries. Some cities in our country have set up ground-source heat pump demonstration projects, but there are still some difficulties in promotion. How do investors understand the economy of ground-source heat pumps? Therefore, the technical and economic analysis of ground-source heat pumps and comparison of various schemes Is necessary. In this paper, economic evaluation methods, the ground source heat pump several investment programs for technical and economic analysis.

Heating, cooling calculation of the main technical parameters are: heating heat load, air conditioning cooling load; economic parameters are: initial investment, annual operating costs, annual total cost, cash flow statement and its related parameters.

1.1 The main economic parameters

1.1.1 Initial investment

Refers to the ground source heat pump system and all parts of the investment: civil fees, equipment acquisition costs, installation costs and other costs (including design fees, supervision fees and contingencies).

1.1.2 The total cost of the year

Refers to the operating costs of various parts of the system, such as water, electricity, fuel costs; sewage charges; management staff salaries and management fees; equipment depreciation costs and equipment maintenance, overhaul and so on.

1.1.3 operating costs

Refers to the total annual cost of equipment depreciation charges deducted.

1.1.4 Cash Flow Statement

Use the cash flow statement method to calculate the relevant economic parameters of investment projects, such as financial internal rate of return, financial net present value, net present value rate and payback period.

(1) Net present value index: It refers to the present value algebra sum of the investment projects discounting the net cash flow of each year to the starting point by the reference revenue, and the formula is:

X NPV is the net present value; A CI is the cash inflow, which refers to the sales revenue from heating or air conditioning, the salvage value of fixed assets and the recovery of working capital; A CO is the cash outflow, including fixed assets investment, working capital, operating cost And sales tax people; ic benchmark rate of return, in this article take ic = 8%; n for the project activity period, record the construction period plus service life.

(2) Net present value ratio: refers to the ratio of the NPV of the project to the present value of the total investment, that is, the NPV that the present value of the unit investment can bring. The formula is:

Where: X NPVR is the net present value of the project scenario; I p is the present value of the total investment in the project scenario; and I t is the investment in year t.

According to the above definition, the project is feasible only when both the NPV and the NPV are greater than zero. In the multi-program choice, under the condition of sufficient funds, the program of large financial net present value first. However, due to different economic conditions, coupled with the size of the financial net present value can only indicate the total profit, did not reflect the impact of investment scale on the utilization rate of funds. Simply using the financial net present value of the largest criteria for program selection, often leads to the evaluator tend to choose a large investment, more profitable programs, while ignoring the less profitable, less investment, but better investment returns, so the net financial performance The value method is generally used in conjunction with the net present value method in order to explain what the net present value of the solution is obtained at. Under the condition of shortage of funds, the indicator of net present value ratio should generally be emphasized.

(3) Investment payback period (including static and dynamic): It is the time needed to offset the total investment of the project by the net income of the project. Static is not considered the time value of money, and the dynamic is to consider the time value of money.

Let PI be the static payback period, calculated as

Let PI "as the dynamic payback period, the formula is

1.2 Calculate the given parameters

1.2.1 weather parameters

Indoor heating design temperature is 20 ℃, indoor cooling design temperature is 27 ℃, heating and cooling outdoor calculation temperature reference to the actual daily average temperature in Harbin in 2000, the number of heating days is 180d, the number of days of cooling 60d, heating 18h Calculation, and then make a comparative analysis; daily cooling hours to the actual number of cooling hours required.

1.2.2 Calculation object

Select the residential building as the calculation object, the maximum heating load for heating 70W / m2, heating area of ​​10,000m2; maximum cooling load of air conditioning to take 70W / m2L5J, air conditioning area according to the actual area of ​​?? the system can be calculated.

1.2.3 ground source heat pump system

Ground source heat pump dual-use, both heating and cooling. A total of three kinds of driving sources were: motor, diesel engine, gas engine; auxiliary heat sources were: electric boilers, oil boilers, gas boilers. Waste heat from diesel or gas engines is recovered when the drive source is a diesel or gas engine. Ground source heat pump heating and heating coefficient to take 3.1, cooling and cooling factors to take 4.0, single air conditioning and cooling coefficient to take 2.9; thermal efficiency of electric boilers to take 1.0, oil boiler and gas boiler thermal efficiency 0.85; diesel and gas engine waste heat recovery Take 0.60. Ground source heat pump buried pipe vertical casing, hole depth of 100m, buried pipe using high density polyethylene (HDPE) pipe, per unit length of the hole heat transfer take 35W / m2. Ground source heat pump life of 15a, the total system heating capacity of 700kW.