Material Insights · Understanding the Material World

Waste heat for drying, water and food: Engineering and integration

When the user depends on someone else's furnace

When the user depends on someone else's furnace What this tab covers Engineering and operating integration: how tightly it is coupled to the host process, how steady the waste stream is, and how hard it is to retrofit.

Every use in this tile depends on a heat source owned by someone else, so co-location, backup heat and matching of seasons are the main engineering issues.

Process interdependence (coupling risk)

Unfavourable

Here the risk runs the other way from most recovery projects: the user depends on the host. If the furnace, power plant or factory stops, the desalination plant, dryer or greenhouse loses its heat and needs a backup boiler or electric heater. A carbon-capture unit is tied to its host's flue gas, so it can only run when the host runs. DOE names the lack of a suitable nearby user as a core barrier to using low-temperature heat.5

Core barrier named by DOE finding a suitable end use for low-temperature heat5

Load factor and intermittency

Mixed

Desalination and carbon capture need steady heat all year and fit continuous hosts. Greenhouses need heat mostly in cold months, and grain drying runs only after harvest, so their utilisation can be low. In a Cadmus sample of US projects, a new grain dryer had by far the longest payback, 7.28 years against an average of 1.31, consistent with short seasonal use.2

Grain dryer payback 7.28 years2 Average payback, 12 heat recovery projects 1.31 years2

Footprint and retrofit complexity

Unfavourable

These uses are new facilities, not add-ons. Desalination plants cost about USD 800 to 1,500 per m3 a day of capacity, and greenhouses or fish farms need land within a short pipe run of the host. Retrofitting an existing factory site is therefore hard; the best fits are large integrated sites. Reliance's Jamnagar refinery hosts India's largest desalination complex: supplier IDE lists 12 MED units of 158,500 m3 a day commissioned 1998 to 2015, and about 230,000 m3 a day of MED in total after later expansion; the brochure does not say what heat drives them.113

Desalination capital cost USD 800 to 1,500 per m3/day1 Reliance Jamnagar MED capacity (vendor figures) 158,500 m3/day in 12 units (to 2015); about 230,000 m3/day total13

Sources

  1. Water Desalination Using Renewable Energy, Technology Brief I12 IEA-ETSAP and IRENA, 2012
  2. Not Just Hot Air: Low-Cost Decarbonization through Heat Recovery (Zahlan and Talan, Cadmus), ACEEE Summer Study on Energy Efficiency in Industry ACEEE, 2021
  3. Waste Heat Recovery: Technology and Opportunities in U.S. Industry (BCS Inc. for US DOE Industrial Technologies Program) US Department of Energy, 2008
  4. Multi-Effect Distillation (MED) brochure (vendor reference list) IDE Technologies, 2022