Solar Energy Perspectives - IEA

Solar Energy Perspectives: Industry and transport
pottery kilns in Morocco, requiring significant amounts of fuel wood; this has led to some
desertification, as the resource is scarce. Moreover, ash regularly destroys up to one-third of
the pottery produced. Clean cooking in a solar oven would significantly improve production,
reduce costs and help preserve the environment. Experiments at Mont-Louis have also shown
that even mid-size solar ovens can easily be used to produce ceramics, glass, as well as
aluminium, bronze and other metals.
The lack of combustion residues is an interesting feature of solar ovens. At high temperatures,
concentrated solar energy can also be used for driving the endothermic reaction that
produces lime (calcination reaction). Running this reaction at above 1 000° C would reduce
emissions of the process by 20% to 40%, depending on the manufacturing plant. It would
also produce very high purity lime for use in chemical and pharmaceutical sectors.
Taibi and Gielen (2010) set the potential for solar heat in the industry by 2050 from
1 550TWh th
/y to 2 220 TWh th
/y. Almost half of this is projected to be used in the food sector,
with a roughly equal regional distribution between OECD countries, China and the rest of
the world, mainly in Latin America (15%) and Other Asia (13%). Costs depend heavily on
radiation intensity, but are expected to drop by more than 60%, mainly as a result of learning
effects, from a range of USD 61/MWh th to USD 122/MWh th in 2007 to USD 22/MWh th to
USD 44/MWh th in 2050.
This estimate for solar heat may seem low, at less than 5% of a total estimated consumption
of almost 50 000 TWh/y for the global industry by 2050. The profitability of solar process heat
is likely to be significantly greater than that of direct solar space heating given that the
demand is, in most cases, roughly constant throughout the year. The case is much closer to
solar water heaters or solar-assisted district heating than to space heating. Difficulties and
competitors, however, should not be underestimated. For example, the pulp and paper
industry meets its large steam needs by using biomass, i.e by-products of the wood preparation
and virgin pulping processes.
Heat pumps, whether closed-circuit pumps, mechanical vapour compressors, or scarcer
absorption heat pumps and heat transformers, operate in the same temperature range as nonconcentrating
solar thermal collectors. They might be preferred in some cases, for several
reasons, such as low solar resource, lack of available space for collectors, or greater flexibility
in being re-used or resold if the industrial process evolves. In many industry sectors (for
example in the glass industry) the low-temperature heat being used is waste heat from highertemperature
processes (run by natural gas in most cases), with or without a temperature lift
provided by heat pumps. Solar heat cannot compete in not-so-sunny places where it cannot
also provide the high-temperature heat.
Fossil fuels are chosen for various industrial processes not only because they provide
energy – they also provide feedstock or are part of the processes. More than one-half of the
energy used in the bulk chemicals industry is for feedstock purposes. Fly ash resulting from
the combustion of coal plays a role in the production of cement, which is why coal is the
main fuel used in this sector, with various wastes eliminated by the high-temperature level –
1 450°C – of the kilns. Similarly, carbon is used as reducing agent for iron ores in blast
furnaces in the process of making steel.
Petroleum refining is a highly energy-intensive process, in which crude oil and intermediate
streams are subjected to high pressure and temperature. The processing of crude oil results
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