Solar energy is widely perceived as a promising technology for electricity generation in remote locations in developing countries. It is estimated that 1Á3 million solar home systems had been installed by early 2000. An estimated one-third of installed systems were backed by foreign donor support in government programmes and twothirds supplied by commercial dealers. The estimated growth in the deployment of solar lanterns is less than for SHS. One out of every 100 households that gain access to electricity in developing countries uses solar power. In spite of these successes, doubts have arisen about the effectiveness and suitability of small PV systems for rural development. Many organisational, ®nancial and technical problems appear to present dif®culties. A literature survey has been conducted to make an inventory of experience with solar PV applications for households in developing countries. The main ®nding is that an adequate service infrastructure is required to make projects viable. Household choice in system sizes is often too restricted in donor-funded projects. Smaller systems sold for cash can be a good alternative to credit systems by offering to increased affordability. Gaps in existing knowledge have been identi®ed, which could be overcome by ®eld monitoring programmes.

Grid connected electrical storage has a high potential to support the transition towards a reliable decentralized and renewable energy supply. It is expected that lithium-ion batteries will play a major role in this transition, because of their high energy density and of the potential capacity that is offered by plug-in (hybrid) electric vehicles. The use of lithiumion batteries in grid support may result in additional degradation. Intelligent control of these batteries can assure that the additional degradation rate is minimized and their utilization is costeffective. It is, therefore, imperative that the intelligent control has an excellent understanding of the aging behavior of the battery, so it can maximize the benefits for the battery owner. Based on this logic, cycle life experiments were performed on lithium polymer cells in which the cell life dependence on the depth of discharge was investigated. Other cell characteristics that were studied include the equivalent series resistance and the efficiency.

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Cost parameters for VSC HVDC transmission infrastructure have been gathered from an extensive collection of techno-economic sources. These cost parameter sets have been converted to a common format, based on a linear investment cost model depending on the branch length and the power rating of cable systems and converter stations. In addition, an average parameter set was determined as the arithmetic mean of the collected parameter sets, and included in the study. The uniform format allowed for a comparison of the parameter sets with each other, which revealed large differences between the cost parameter sets. The identified disparity between the parameter sets reflects a high level of uncertainty which can only in part be explained by a varying focus and modelling approach of their sources. This implies limitations regarding the validity of the parameters sets as well as of the results from grid expansion studies carried out on the basis of these parameter sets. Comprehensive cost reference data has been collected from realised and contracted VSC HVDC projects (back-to-back, interconnector, and offshore wind connection). The cost parameter sets have been evaluated against the reference project cost data. This evaluation has again shown large variations between the parameter sets. On average, the cost for back-to-back systems are slightly underestimated, interconnectors are overestimated, and offshore wind connections are heavily underestimated. To clearly state the validity and limitations of this comparison and evaluation, the applied methodology with its compromises and drawbacks is discussed in detail. Considering the interest in and momentum of offshore grid development, as well as the number of offshore grid investment and evaluation studies being conducted, both the availability of reliable cost reference data and the validity of investment model cost parameters need continuing attention

A large number of offshore wind farms and interconnectors are expected to be constructed in the North Sea region over the coming decades, creating substantial opportunities for the deployment of integrated network solutions. Creating interconnected offshore grids that combine cross-border links and connections of offshore plants to shore offers multiple economic and environmental advantages for Europe's energy system. However, despite the growing consensus among key stakeholders that integrated solutions can be more beneficial than traditional radial connection practices, no such projects have been deployed yet. In this paper we quantify costs and benefits of integrated projects and investigate to which extent the cost-benefit sharing mechanism between participating countries can impede or encourage the development of integrated projects. Three concrete interconnection case studies in the North Sea area are analyzed in detail using a national-level power system model. Model outputs are used to compute the net benefit of all involved stakeholders under different allocation schemes. Given the asymmetric distribution of costs and benefits, we recommend to consistently apply the Positive Net Benefit Differential mechanism as a starting point for negotiations on the financial closure of investments in integrated offshore infrastructure.