It is now more than a decade since distributed generation (DG) began to excite major interest amongst electric power system planners and operators, energy policy makers and regulators as well as developers. This paper presents an overview of the key issues concerning the integration of distributed generation into electric power systems that are of most interest today. The main drivers behind the focus on DG integration, especially of the renewable type, in many countries around the world are discussed. A synopsis of the main challenges that must be overcome in the process is presented. Particular emphasis is placed on the need to move away from the fit and forget approach of connecting DG to electric power systems to a policy of integrating DG into power system planning and operation through active management of distribution networks and application of other novel concepts. The paper also analyses the repercussions in transmission system operation and expansion that result from the connection of large amounts of DG of different energy conversion systems focusing on issues related with impacts in steady state operation, contingency analysis, protection coordination as well as dynamic behaviour analysis. A discussion on the possibility of provision of ancillary services by DG is also included. Some results from studies performed in the interconnected Portuguese transmission system are presented and discussed. Some of the opportunities that could be exploited in support of the integration and hence greater penetration of DG into electric power systems are also explored.

The primary driver for development of organic photovoltaic (OPV) technologies is the prospect of very low cost module manufacture leading to affordable solar electricity. This paper presents an economic assessment of OPV based on an existing pre-industrial manufacturing process and the associated detailed material inventory. Using life cycle costing techniques, the life cycle investment cost for a 1kW p , grid-connected OPV system is calculated, taking into account the materials, direct process energy, labour, balance of system components, design and maintenance costs. Assuming values for the performance ratio of the PV system, insolation level, inflation and interest rates, the levelised electricity cost (LEC) is calculated. Under an average solar irradiance of 1700 kWh/m 2 /year, typical of southern Europe, a LEC of between 0.19 V/kWh and 0.50 V/kWh was calculated for a 1kW p system, based on modules containing 7% efficient cells and assuming a 5 year module lifetime. The OPV module is found to make up the majority of the system cost while the material costs constitute the largest contribution to the cost of the OPV module. The influence of OPV module lifetime is studied using sensitivity. This paper demonstrates that competitive solar electricity from OPV is within reach if efficiencies of ca. 7% already demonstrated in lab scale devices can be achieved in large area modules and if lifetimes of at least 5 years can be achieved.

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