Waste heat used for production of precast concrete
Researchers develop new components in the project ENBELAT. To use the hydration heat they provide concrete precast molds with a heat recovery and save the heat in a latent heat storage. This increases the quality and helps the energy consumption to be reduced 45 percent.
|Project status||Project completed|
|Type of storage||Sensible heat storage (concrete), Latent heat storage (Paraffin)|
|Auxiliary equipment||Sensor system|
|Storage capacity||4.500 x 103 kJ (bzw. 4.500 MJ)|
|Energy storage density||4.186 kJ/m³|
|Number of cycles||4.800|
|Storage time||Short (hours to days)|
|Charging temperature||60 °C|
|Discharging temperature||50 °C|
|Project duration||October 2012 until September 2015|
The project is aimed at an approximately 45% decrease in energy consumption when producing prefabricated concrete parts in a way accelerated by heat. This reduction is contributed to "Energy savings and energy efficiency“ within the scope of the 6th Energy Research Programme, thereby also providing an increase in product quality. For this purpose, a technological and plant system for recovery and storage of waste heat from industrial processes (hydratation heat and thermal heat for heating) and its utilisation in the operational process in a way meeting the demands are developed.
In this project, entirely new and innovative plant components for process heat extraction (mould for prefabricated concrete elements with heat recovery), storage (latent heat storage) and reintroduction of the process heat obtained (pre-heating hot water of the initial materials for conrete in the floodable silo or, as an alternative, in the concrete mixing plant) are developed, designed and tested in the plant system.
Better quality and longer life
Taking the state of the art as reference base, the energy efficiency of the production process is achieved by sustainable energy savings of approx. 80 % when the concrete is hardened in a way accelerated by heating. As a result, the CO2 balance of the product is significantly improved. The product is significantly upgraded thanks to an increase in structure quality and since the elements are free of ruptures. This result, in turn, leads to higher concrete element life due to thermal process control/ inspection (curing, after-treatment).
The prefabricated concrete parts produced by means of the technological and plant system to be engineered become much more profitable due to energy savings and added value, as well as due to cost reduction and higher serviceability.
Having successfully implemented the R&D topic, the production of prefabricated concrete parts will be acknowledged as a high technology. The interdisciplinary teamwork of SMEs (plant engineering firms, mould making firms and producers of prefabricated concrete elements) with an appropriate research institution is a necessary precondition for the implementation of the project.
Save hydration heat and recirculate heating
With the system solution to be designed in the ENBELAT project, the producers of prefabricated concrete elements of any company sizes — in this case also for SMEs — are offered the following opportunities:
- to produce at maximal energy efficiency,
- to sustainably enhance the structure quality of the concrete elements generated by means of process control/ inspection and innovative technology,
- to produce according to high quality standards and
- to tremendously reduce investment return.
In contrast to state of the art, the system solution aspired makes it possible to produce with less than 20 % of external energy to heat up the moulds, and refined structures are achieved simultaneously. These savings are enabled by the storage and recovery/reintegration of hydratation heat and thermal heat into the process.
A central subject of research is the extraction of process energy by developing a battery mould for reinforced concrete slabs as heat exchanger interacting with a heat storage to be developed for intermediate storage and controllable heat integration into and extraction out of the manufacturing process in connection with the design and test of the concrete recipes customised for the process under development.
Improved thermal energy management
By contrast with the state of the art practiced, the ENBELAT project is not only aimed at covering a material percentage of the thermal energy needed for the technology from the process' waste heat, which is available and to be removed anyway, but also to significantly enhance product quality thanks to thermal energy management.
The forecasted savings are referred to the production volume parameters for prefabricated flat concrete elements, which were manufactured in the FRG in 2009 - a volume of 32 Mio m³ - , and a percentage of 20 % assumed as prefabricated concrete parts produced in heated moulds, as well as to the calculations of the energy balance of the total process. These reference values permit an extrapolation of feasible annual energy savings of approximately 24 GWh/a, as well as an approximately 15.000 t/a reduction of annual CO2 emissions supposing a proportional use of the production and storage technologies to be developed. Compared to other estimates, these values (savings) correspond to the electricity consumption of approximately 14,400 private individuals in 2009.