BENCHMARK WITH H2A CODE

The H2A is a spreadsheet code developed in the U.S. Department of Energy (DOE) under the Hydrogen and Fuel Cells Program. A description of the code can be found in Chapter 3.

4.3.1. Benchmark cases

During first RCM of the CRP “Examining the Techno-Economics of Nuclear Hydrogen Production and Benchmark Analysis of the IAEA HEEP Software”, five combinations of nuclear power plant and hydrogen generating processes were identified for benchmarking of the IAEA software tool HEEP (Minutes of 1^st RCM on CRP Examining the Techno-Economics of Nuclear Hydrogen Production and Benchmark Analysis of the IAEA HEEP Software). During this meeting, it was agreed to use following information on technical features, construction time and cost components provided in Table 43 for estimation of hydrogen cost.

TABLE 43. DETAILS OF CASES IDENTIFIED FOR BENCHMARKING EXERCISE

Case-1 Case-2 Case-3 Case-4 Case-5

Common parameters for both nuclear power plant & hydrogen production plant

Capacity factor 93% 93% 93% 90% 90% Decommissioning cost 2.8% of

Capital cost

Process type Electrolysis Electrolysis Electrolysis HTSE S–I Hydrogen generation 4 kg/s 8 kg/s 12 kg/s 4 kg/s 4 kg/s Decommissioning cost 10% of capital

cost 10% of

As per the information compiled during first RCM, the cost for disposal of nuclear fuel is considered to be included in the annual fuel cost. Further, the thermal efficiency of nuclear power plants in Cases 1 to 3 is considered as 33% and efficiency of electrolyser to generate hydrogen is considered as 79% w.r.t. electrical energy. In the absence of relevant information, default values for techno-economic parameters given in Table 44 are considered for the assessment using HEEP.

TABLE 44. DETAILS OF DEFAULT VALUES OF PARAMETERS

Fiscal parameters

1. Nominal discount rate 5%

2. Inflation rate 1%

3. Equity to Debt ratio 70:30

4. Interest on borrowings 10%

5. Tax rate 10%

6. Depreciation period 20 years

7. Return period for market borrowing 40 years

8. Cash flow during construction period Equally distributed Important time periods

9. Operating life 40 years

10. Cooling before decommissioning 2 years

11. Decommissioning period 10 years

During the first RCM, a lump sum of annual fuel cost for the nuclear power plant was provided. However, HEEP models the fuel cost through the cost of fuel per unit weight. Thus, based on the anticipated initial fuel load as well as annual fuel consumption, the fuel cost per kg was derived from the annual fuel cost given in Table 45. The values of initial fuel load and annual fuel consumption considered for all five cases are given in Table 45. For batch type annual loading, it is further assumed that one-third core is replaced during each re-loading, as done for many operating PWRs.

TABLE 45. DETAILS OF FUEL COST PARAMETERS

Case-1 Case-2 Case-3 Case-4 Case-5

Initial fuel load per

unit 27 000 kg 54 000 kg 75 000 kg 14 000 kg 18 000 kg

Annual fuel consumption per

unit 9000 kg 18 000 kg 25 000 kg 5000 kg 6000 kg

Rate of fuel $/kg 1850 1365 1260 3660 5535

Hydrogen generation in three cases, viz. Case-1 to Case-3, employs the conventional electrolysis process. This process requires energy in the form of electricity only. The nuclear power plant co-located with hydrogen generation plant is considered to produce only electricity for these three cases.

Case-4 deals with a combination of nuclear power plant and hydrogen plant which operates on high temperature steam electrolysis process. The process requires electricity. However, no information on electricity required by the process was available. In absence of this information, supply of heat energy alone from nuclear power plant is considered in HEEP. In such circumstance, user has to provide energy usage cost to meet the electricity demand to operate hydrogen plant. However, it is further assumed that the cost of electricity purchase from grid is included in the total O&M cost. This is assumed as the O&M cost per unit of hydrogen produced for hydrogen plant based on high temperature steam electrolysis was found to be 5 time higher than plants operating on conventional electrolysis process. Hence, the energy usage cost, which covers the cost of external electricity usage at market rate, has not been considered separately, but considered to be included in the annual O&M cost. It should be noted here that this cost is expected to be substantial contributor to the final cost of hydrogen.

Hydrogen generation in Case-5 uses the high temperature S–I process. As per the information compiled, the hydrogen generation plant consumes electric power of 42.8 MW(e). It is assumed that the electricity is obtained from the grid at $0.072 /kWh, in both H2A and HEEP.

4.3.2. Benchmark results

With the same inputs, hydrogen cost is estimated using another software tool H2A. This tool was downloaded from the internet. Table 46 gives comparison between results generated by HEEP and H2A.

TABLE 46. COMPARISON OF HYDROGEN COST ESTIMATED BY HEEP AND H2A

Case-1 Case-2 Case-3 Case-4 Case-5

HEEP results $5.44 $4.13 $3.48 $2.54 $2.97

H2A results $5.32 $4.03 $3.39 $2.21 $2.53

The levelized hydrogen cost estimated by HEEP closely matches with that estimated by H2A.

The range of variation is from $0.14 to $0.03 per kg of hydrogen.

In Cases 1 to 3, the construction period specified is 5 years. H2A cannot account for construction period more than 4 years. Hence, the cost estimated by H2A model is with an assumption of 4 years construction period while that from HEEP is with 5 year construction period. For Cases 4 and 5, where construction period considered is same for both HEEP and H2A estimations, the match between the results obtained from H2A and HEEP are in excellent agreement being within 16%.

When the construction period for Case 1 to 3 is reduced to 4 years in HEEP, it was observed that the match improves. The variation reduces from $0.14 to $0.05. The comparison is given in Table 47.

TABLE 47. COMPARISON OF HYDROGEN COST ESTIMATED BY HEEP AND H2A

Case-1 Case-2 Case-3

HEEP results $5.37 $4.08 $3.44

H2A results $5.32 $4.03 $3.39

These results indicate that the underlying mathematical models and the programming of HEEP are accurate, and flexible enough, to analyse any nuclear hydrogen generation scenario.