Francis G.N. Li

Solid-wall U-values: heat flux measurements compared with standard assumptions

The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1u2009Wm−2u2005K−1. A re-analysis (based on 40 brick solid walls and 18 stone walls) using a lumped thermal mass and inverse parameter estimation technique gives a mean value of 1.3u2005±u20050.4u2005Wm−2u2005K−1 for both solid wall types. Among the many implications for policy, this suggests that standard UK solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation. For stock-level energy modelling, changing the assumed U-value for solid walls reduces the estimated mean annual space heating demand by 16%, and causes a proportion of the stock to change Energy Performance Certification (EPC) band. The analysis shows that the diversity of energy use in domestic buildings may be as much influenced by heterogeneity in the physical characteristics of individual building components as it is by variation in occupant behaviour. Policy assessment and guidance material needs to acknowledge and account for this variation in physical building characteristics through regular grounding in empirical field data.

Achieving net-zero emissions through the reframing of UK national targets in the post-Paris Agreement era

The Paris Agreement provides an international framework aimed at limiting average global temperature rise to well below 2°C, implemented through actions determined at the national level. As the Agreement necessitates a ‘net-zero’ emissions energy system prior to 2100, decarbonisation analyses in support of national climate policy should consider the post-2050 period. Focusing solely on mitigation objectives for 2030 or 2050 could lead to blindsiding of the challenge, inadequate ambition in the near term, and poor investment choices in energy infrastructure. Here we show, using the UK as an example, that even an ambitious climate policy is likely to fall short of the challenge of net-zero, and that analysis of the post-2050 period is therefore critical. We find that the analysis of detailed, longer term national pathways which achieve net-zero is important for future reassessment of ambition under Nationally Determined Contributions (NDCs).

Hydropower in China

Abstract This paper provides an overview of the power sector in China during the past 40xa0yr, with a special emphasis on hydropower. The article includes a description of the power sector in China and the main problems it is now facing. The alternatives for Chinas peaking requirements are also described, with mention of both pumped storage and increased hydro capacity as important options. Hydropower has very important side benefits, and these are also described. The article finally summarizes the main concerns of the Chinese Government in sustaining its economic development, and describes the future role that hydropower will play in this development.