The WASP (Wien Automatic System Planning Package) model permits the user to find an optimal expansion plan for a power generating system over a long period and within the constraints defined by the planner, which is maintained by the IAEA (International Atomic Energy Agency) [1]. So far four versions of WASP have been created which has been distributed to several hundred users. The model is freely available to IAEA member states and requires 4 to 6 weeks of training. There is support forum specifically for WASP at [2].

In WASP the optimum expansion plan is defined in terms of minimum discounted total costs. Each possible sequence of power plants that could be added to the system (expansion plan or expansion policy) and that meets the selected constraints, is evaluated by means of a cost function composed of: capital investment costs, fuel costs, operation and maintenance costs, fuel inventory costs, salvage value of investments and cost of energy demand not served. The entire simulation is carried out using 12 load duration curves to represent each year, for up to a maximum duration of 30 years. As a starting point, WASP requires representation of the existing system defining the technical, economic and environmental characteristics of all existing power plants: note that only the electricity sector is considered. These characteristics include: plant capacities, minimum and maximum operating levels, heat rates, maintenance requirements, outage rates, fuel and operation costs, emission rates, etc. Conventional fossil-fuel, nuclear and biomass power plants can be simulated. In addition wind, wave, tidal and hydro power can be considered as well as PHES. For the given yearly future demand for electricity, it explores all possible sequences of capacity additions that will match this demand and at the same time satisfy all the constraints. The constraints can be based on achieving a certain level of system reliability, availability of certain fuels, build-up of various technologies, or environmental emissions. The sequences of capacity additions are first screened and those that satisfy the constraints, called feasible configurations for expansion of the system, are selected. The operation of a system for all these configurations is then simulated using a probabilistic simulation technique, which takes into account the failure probabilities of the plants and produces unit dispatch schedules to meet the given load. Available units are dispatched according to their marginal production costs. The generation, fuel requirement and environmental emissions of each unit are calculated and checked against any limitations imposed externally. Finally, a dynamic programming algorithm traces the optimal sequencing of capacity additions.

WASP has previously been used to evaluate the potential of biomass power generation [3], to examine the future role of nuclear power in Korean [4], and to identify the least cost expansion plan for Thailand in order to evaluate its future dependence on natural gas [5].


  1. Department of Nuclear Energy: Planning & Economic Studies Section (PESS), International Atomic Energy Agency, 13th June 2009, http://www.iaea.org/OurWork/ST/NE/Pess/PESSenergymodels.shtml
  2. ADICA Energy Forum, ADICA, 22 April 2010, http://www.adicasupport.com/wrapper/energy_forum.html
  3. Santisirisomboon, J., Limmeechokchai, B. & Chungpaibulpatana, S., Impacts of biomass power generation and CO2 taxation on electricity generation expansion planning and environmental emissions. Energy Policy,29(12), pp. 975-985, 2001.
  4. Lee, Y. E. & Jung, Y. B., Challenges of nuclear power for sustainable role in Korean energy policy. Energy Conversion and Management, 49(7), pp. 1951-1959, 2008.
  5. Nakawiro, T., Bhattacharyya, S. C. & Limmeechokchai, B., Electricity capacity expansion in Thailand: An analysis of gas dependence and fuel import reliance. Energy, 33(5), pp. 712-723, 2008.