Low-Grade Heat: Issues to be Dealt With

Abstract

As it was concluded by International Energy Agency (IEA, 2008), in 2005, manufacturing industry was globally consuming the most energy, with 33% share, followed by households (29%) and transport (26%). Its carbon dioxide emissions share was also biggest, constituting 38%. From 10% to 50% of this energy is lost with waste heat to the environment. About 60% of this energy is going as low-grade heat. The typical sources of low-temperature heat are presented in Table 2.1.The temperature and other conditions of the industrial waste heat are highly dependent of particular industry. It can be in the form of contaminated steam in petrochemical and refining industry at the level about 150 °C or cooling water about 30 °C-55 °C. In food and beverage industries, the level can be about 80 °C. Globally, the largest savings potentials can be found in iron and steel, cement, and chemical and petrochemical sectors. On average, Japan and the Republic of Korea have the highest levels of industrial energy efficiency, followed by Europe and North America. Energy efficiency levels in developing and transition countries show a mixed picture. Generally, the efficiency levels are lower than in Organisation for Economic Cooperation and Development (OECD) countries, but, where there has been a recent, rapid expansion using the latest plant design, efficiencies can be high (according to IEA, 2013). Final energy use in industry was 116 EJ in 2005. The useful energy and the lost energy in major industrial sectors of the United States are shown in Figure 2.1.The divisions of waste heat recovery potentials between different processes most promising for heat recovery chemical and oil refining industries, according to the analysis of Pellegrino et al. (2004), are presented in Tables 2.2 and 2.3.The chemical, petrochemical and other heavy industries are distributed unevenly between different countries in the world; food and beverages sector are present rather evenly more closely following the distribution of the world's population. There is significant potential to recover waste heat from food and beverage industries, as shown by Law et al. (2013). Only in the United Kingdom this sector has about 10.08 × 10 15 J of wasted low-grade heat available for heat recovery. The use of this heat is similar