Sustainable Heat & Power Europe GmbH

Process Steam

Introduction

energy use

In 2007, the industrial sector of the member states of the European Union (EU-27) had a demand for thermal energy of 2.600 TWh (Source: Eurostat). This equates to 69.3 % of the total energy demand. That figure is more than twice as high as the demand for electricity. A high amount of this thermal demand is consumed on a temperature level below 400 °C. It is safe to assume that, in target countries for solar thermal applications, the situation in the industry is not significantly different from these European averages.

Configuration

In industrial applications, process steam is typically distributed in form of saturated steam. This occurs on a pressure level determined by the required saturation temperature, which corresponds to the highest-needed temperature in the system. This steam is either directly supplied by a fossil-fired boiler or by a CHP (combined heat and power) configuration of a steam turbine. In that case, the boiler supplies the turbine and the steam is taken from either the exhaust of a back-pressure turbine (and/or extractions at a higher pressure level).

In both of these cases, the fossil-fired boiler can be partially replaced by a solar thermal collector field, or even fully, provided that a suitable thermal storage system is applied. The solar generated steam may therefore completely replace valuable fossil fuel. At the very least, it saves fossil energy and thus reduces CO2 emissions and the carbon footprint of the produced goods.

Areas of application

Process steam serves industrial branches (e.g., the chemical industry, mining operations, the food processing industry or the textile industry) with its variety of vital applications:

  • Process Steam and Process Heat
    Process heat is used directly in industry to provide the thermal energy for endothermic processes (be it a required heat input for chemical reactions or heat for boiling, washing, drying, or sterilisation).
  • Cooling
    Another major application for process heat is its opposite: the provision of cooling. Here, the steam/heat is used to drive absorption chilling machines. The working principle is similar to that of the common compression chillers. The difference is that the thermal energy takes over the role of the electrically driven compressor, thereby saving valuable electricity. Absorption chillers can be single, dual-stage or even triple-stage. Lithium bromide commonly acts as absorption media for air-conditioning systems, and ammonia is used for dual- or triple-stage chillers in refrigeration applications.
  • Thermal Seawater Desalination
    A third application for process steam is the desalination of salty or brackish water. This is a very attractive option, as itís generally the regions with high solar irradiation that face supply problems with potable water for inhabitants and agriculture. One technology that uses thermal energy as the driver is the MED (Multi-effect Desalination) process. The process steam/heat used in the first effect of a MED evaporates brine, and the emerging clean vapour is then used in the next stage. (An increasing vacuum in the different effects drives this process.) One key advantage of the MED process is that it only requires heat input at relatively low temperature (70-80 °C), so itís able to use the waste heat of a combustion motor, the exhaust heat of a steam turbine, or the heat collected in ordinary flat-plate or vacuum-tube solar collectors.

Advantages

Solar process steam has a range of attractive advantages. It can be easily introduced into existing plants, provided sufficient space for the solar collector is available on the roof or nearby. Integration into the steam-supply system is simple, and the existing infrastructure (boilers, etc.) will guarantee the safe supply of process steam, even at times with insufficient solar radiation. Solar steam saves fossil fuel, thereby reducing CO2 emissions in industries with very high energy demand. This reduces the carbon footprint of the goods produced. In combination with a steam turbine, solar-generated steam may be applied as an electricity-generating process first, while the required process steam is then taken from exhaust or extraction points. This combined heat and power approach usually offers attractive economic benefits for the plant operator.

Our Service

As well as its many years of technical expertise, SHP Europe retains excellent resources in cooperation with our network of regional and international partners. We offer the following services and supplies:

  • Solar Measurement Campaigns
  • Site assessment and project development services
  • Energy audit, feasibility studies and analyses of the generation potential, technical concept and economic forecast for the solar process steam plant
  • Engineering services and project management for the integration of the solar process steam supply into the existing plant