ICE - Institution of Civil Engineers - Virtual Library

For centuries, geothermal energy has been used for bathing, cooking and space heating. More recently, district heating, industrial processing and geothermal heat pumps have become part of the direct-use mix. Geothermal electric power generation began in Italy in 1904, with the first commercial plant operational in 1913. Presently, the total installed global capacity for direct use is 29 000 MW_t, producing 76 000 GW h/year in 72 countries; the installed capacity for electric power is 9700 MW_e, generating 60 000 GW h/year in 24 countries. Recent trends are to maximise the use of geothermal resources in a combined heat and power project. Geothermal resources of around 100C have been used in binary (organic Rankine) cycle plants and then cascaded for district heating. Geothermal energy is considered to be both renewable and sustainable as a ‘green energy’ resource, but certain environmental aspects must be considered and mitigated.

The production of synthetic natural gas (SNG) via biomass gasification constitutes a promising option for biofuel manufacture due to its high conversion efficiency and diversity of end-use opportunities in different sectors. This paper presents a critical review of possible feedstock conversion paths from biomass to SNG via gasification. Similarities with research and development issues for coal gasification projects for SNG production are identified and the state of the art for the bottleneck stages of the conversion is discussed. The need for tools to improve process efficiency is clearly shown; the pinch methodology is a powerful tool for process integration and is of particular interest in this regard. Biofuel production processes often deliver multiple products and services such as heat, electricity and other by-products and are often referred to as polygeneration or biorefinery concepts. To take into account the multiple possible products and services resulting from SNG production, it is necessary to carefully define appropriate process performance indicators. For a sound assessment of the future potential of biomass-based SNG production, an evaluation of the most promising process alternatives against a background of possible future energy market scenarios is necessary.

A critical review of the literature relating to government policy and behavioural aspects relevant to the uptake and application of microgeneration in the UK is presented. Given the current policy context aspiring to zero-carbon new homes by 2016 and a variety of minimum standards and financial policy instruments supporting microgeneration in existing dwellings, it appears that this class of technologies could make a significant contribution to UK energy supply and low-carbon buildings in the future. Indeed, achievement of a reduction in greenhouse gas emissions by 80% (the UK government’s 2050 target) for the residential sector may entail substantial deployment of microgeneration. Realisation of the large potential market for microgeneration relies on a variety of interrelated factors such as microeconomics, behavioural aspects, the structure of supporting policy instruments and well-informed technology development. This paper explores these issues in terms of current and proposed policy instruments in the UK. Behavioural aspects associated with both initial uptake of the technology and after purchase are also considered.

Integration of different types of small-scale embedded generators (SSEGs) in the UK electricity supply system has become a key issue for distribution network operators, policy makers, energy producers and the research and development community. When regarded as separate entities, SSEGs offer minimal technical, economical or environmental benefits. However, intelligent coordination of large numbers of SSEGs coupled with energy storage and demand-side management techniques have the potential to maximise these benefits. This paper introduces the small-scale energy zone (SSEZ) concept, which aims to facilitate the proliferation of SSEGs by maximising their potential commercial and environmental benefits, while also ensuring that the associated technical challenges are overcome. A distributed control approach, realised through multi-agent systems technology, is proposed in order to satisfy the specific control requirements of an SSEZ. Moreover, an application of the proposed agent-based approach to the experimental SSEZ at Durham University is presented, focusing on overcoming steady-state voltage-rise issues. Results demonstrating the deployment of direct generation agents are presented and discussed, showing that active network management schemes employed within SSEZs have the potential to increase system performance, while also increasing the annual energy yield of the connected SSEGs.