W-TEMP code started its life almost ten years ago when TPG decided to move to the study and optimisation of complex and fanciful energy systems which need to be technically and economically feasible in practise and not only in mind. This reason convinced us to develop a detailed software tool for the complete and automatic thermoeconomic analysis of power and cogenerative plants of different type, concept and size.
From the beginning, the basic idea was to create a modular program in order to allow a free development by all the users: such a happy starting point led to a code that, at present, offer you more then 90 modules, is capable of simulating several types of energy plants (can’t say “all” because it is impossible to know what the future is preparing…) from conventional systems (e.g.: combined cycle) to advanced concepts (humid air cycle, fuel cell hybrid system, biomass gasification integrated plant, etc…), automatically provides the user with detailed thermodynamic, exergetic, economic data about both the internal structure of the layout and the plant as a whole. Of course, the obtained results are as accurate as the basic assumptions for the thermodynamic perfomance and component costs the user has to make.
As usual, it is always a good practice mistrusting straightforward results: indeed, it is better appreciate and believe achievements coming from the efforts and experience of a team of engineers. This is what we do. So far, we had several occasions to test W-TEMP reliability with industrial and academic data from the field: this allows us to use W-TEMP as our “rule of thumb” for energy plant assessment from the thermoeconomic point of view.
W-TEMP allows the thermoeconomic and exergoeconomic analysis of a large number of energy cycles such as the following to be obtained: steam, gas turbine, combined, and advanced cycles (mixed gas-steam cycles, biomass gasification integrated plant, fuel cells – SOFC and MCFC – and hybrid cycles, partial oxidation cycles, chemical recovery cycles, integrated solar combined cycles). The system to be calculated is defined as an ensemble of interconnected components.
Operating characteristics and mass and energy balances of each component, in the on-design state, are calculated sequentially until the conditions (pressure, temperature, mass flow, etc.) at all interconnections converge on a stable value. After the thermodynamic calculation, the thermoeconomic analysis is performed: at first each component purchase cost is defined through the use of cost or costing equations, therefore the internal thermoeconomic and exergoeconomic analysis is carried out through the cost and exergy balances of each module.
It is possible to calculate the internal irreversibility of each component (that determines an exergy expenditure) and its capital cost (that determines a monetary expenditure). Thermoeconomic results are given at two different levels: at the inner level as an estimate of the average unit cost (c), the unit exergetic cost (k*) and the marginal cost (?) at each connection; at the outer level as an evaluation of the thermal efficiency, the generated power, the generated heat, the electrical and thermal energy costs. In addition, it is possible to carry out plant through-life cost analysis, calculating financial parameters such as internal rate of return, payback period, net present value and others. In the end plant thermodynamic and economic features are completely and fully described.
The W-TEMP code is also provided with an optimisation tool that allows energy system thermoeconomic optimisation to be obtained with different objective functions: the most important are thermal efficiency and the cost of electricity. The non-linear optimisation algorithm has been recently upgraded with the introduction of a genetic algorithm.
In the W-TEMP code, besides the complete thermoeconomic assessment, also the environomic analysis of power plants is available. The criteria that will influence the evolution of the energy market this century will be based on the need to preserve the environment (both locally and globally) through new technologies and sustainable use of existing resources. This need is also ratified by the guidelines of the various Framework Programs of the European Community and by international agreements such as the Kyoto Protocol. In particular, the global warming problem, linked to CO2 emissions, requires an energy policy approach at an international level devoted to CO2 regulation: the energy policy should aim at punishing the inefficient use of fossil energy sources that determines a larger emission of CO2 than a more efficient use.
W-TEMP allows the user to evaluate the effects on, for example, the final cost of electricity and the internal rate of return of the plant caused by the introduction of charges on pollutant emissions or of fuel taxation. In this respect, W-TEMP is also a powerful tool for evaluating the advantages and drawbacks of policy actions from a microeconomic and macroeconomic perspective. W-TEMP is provided with the complete Carbon Exergy Tax (CET) procedure, proposed by TPG as an effective rule to control CO2 emissions penalising the most inefficient systems.