Free heating, temperature conditioning at half price - Reisner AG

Free heating, temperature conditioning at half price
Reisner waste heat utilization reduces operating costs and CO2 emissions
Energy costs in the plastics processing industry have been continually spiraling for years. An
end to this trend is not in sight. On the contrary: manufacturers who want to lower production
operating costs to a tolerable level and keep them there have to actively develop energy
saving potentials. Heat is playing an ever increasing part in this respect. Unwanted in
production, it is needed at other locations, where it has to be generated at high cost. This is
where customized solutions for heat recovery come into play, such as those utilized by
Reisner AG Kältetechnischer Anlagenbau to achieve huge market success worldwide.
Reisner systems turn waste heat into usable heat and therefore significantly reduce the
required energy consumption.
When cold water is used in the plastics processing industry to cool tools or hydraulic
components, a cooling machine generally has to be used to bring the water to the right
temperature. The cooling machine in such applications always functions as a heat pump.
This means that it collects the thermal energy from locations where it is not needed, heats it
to a higher temperature and then delivers it to another location. This process usually makes
use of a condenser, which dissipates the heat into the environment. Not only the energy
generated during production is affected, but also the waste heat generated by the operation
of the cooling machine itself.
Reisner AG develops such cooling systems and has recognized that there are many
interesting ways to use energy not needed in production. Instead of wasting this energy, it
makes sense to reuse it within the plant. That is why Reiser AG for years has offered
systems that make heat from production and cooling usable for heating buildings. Now the
company has developed an entirely new concept that goes one step further than the
previously available solutions and opens up even more interesting perspectives.
Improved concept for more possibilities
In the conventional method for recovering heat, the waste heat is taken up by a heating
water circuit and distributed in the building by means of an air heating system. This method
already saves a great deal of energy. If the cooling machine has a cooling capacity of 100
kW and a compressor drive output of 138 kW, then total recovered heat of 138 kW is
available. If this is put into relation to the electric energy needed for the compressor – namely
38 kWh – then there is a potential of 138/38, or 3.6 kWh of heat for each kWh of electric
energy. A comparison with direct electric heating, in which one kWh of electricity is needed
for each kWh of heat shows how lucrative this gain is. In addition, the cooling machine for
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production of the cold water is operating in any case and the waste heat is therefore
available at no extra expense.
Ventilation units distribute the
heat to where it is needed.
They can be adapted to
specific room conditions.
However, the standard technologies for heat recovery used in the past do not fully exhaust
the potentials for saving. Some of the valuable energy is lost. Therefore, only heating water
with a relatively low temperature can be supplied. This represents a limitation in the heating
of the plant. The low-temperature heating water can only be used for air duct and floor
heating systems. If older heating radiators in offices and halls are used for heating to a
comfortable temperature, the temperature of the water has to be much higher. In order to reuse
energy directly in production and to generate heat by reusing waste heat, an even hotter
heating medium is necessary. This application is especially attractive, because temperature
conditioning units normally are operated directly with electricity and only one kWh of heat can
be generated for each kWh of electricity.
An effective cost-benefit ratio
In the continued development of its heat recovery concept, an important focus for Reisner
AG was that the water provided by the systems has to be as hot as possible. This can result
in problems with efficiency, depending on the desired temperature: the system may have to
achieve a higher condensation temperature. Consequently, the compressor requires more
electric power. Therefore, not only the potential benefit of the heat recovery increases, but
also the expense for achieving it – and this ratio has to be considered for each individual
solution.
The method applied by Reisner AG is based on the perfect control of all thermodynamic
processes in the system. This makes it possible to minimize losses and to utilize nearly one
hundred percent of the waste heat. High heating medium temperatures can also be achieved
without necessarily having to increase the condensation temperature. This limits the power
consumption of the cooling system. A key technical concept is the central bundling of the
waste heat stream. This is achieved by installing a heating circuit that circulates through the
condenser and collects all of the waste heat. If not all of the heat is needed – for example, if
it is to be used for heating purposes and the outside temperature is high enough that no
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Efficient all-rounder: this
Reisner cooling system is
optimized for use with heat
recovery.
heating is necessary – a dry cooler dissipates the heat into the environment. Otherwise, the
heating medium stream is bundled in a special tank, where the waste heat is stored and can
easily be tapped for the respective application. The heat exchangers used in the system are
also important. They are designed especially for heat recovery and therefore achieve
optimum results.
Convincing figures
The success of this concept is demonstrated by numerous reference systems from Reisner:
Dr. Schneider Kunststoffwerke GmbH, located in Kronach in Bavaria, even implemented the
conversion of its cooling unit to a waste heat recovery system as a pilot project sponsored by
the Federal Ministry for the Environment and Conservation. At the Russian plant of the
window profile manufacturer Deceuninck the Reisner system provides for fully adequate
heating of the building despite extreme winter temperatures – with no additional energy
costs. The surface finishing specialist Vollmerhaus of Plettenberg also now benefits from the
free available heat energy with the help of a Reisner system.
Large halls can also be
heated easily with free
available heat.
Even with a cooling unit with a cooling capacity of 155 kW and a compressor capacity of 42
kW – therefore with total waste heat of 197 kW – the heat recovery is sufficient to heat an
area of 2,500 sq. meters all winter long – at no additional cost. The effect on the company’s
overall energy costs is demonstrated concretely by converting the efficiency of the system
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into fuel oil saved. The system has a calorific value of 9 kWh per liter. The estimated waste
heat stream of 197 kW is therefore equivalent to 21.9 liters of fuel oil per hour. If a liter of fuel
oil costs 0.60 EUR, then heating the hall with waste heat saves more than 13 EUR for each
hour of operation as compared with oil heating. Therefore, the amortization period for the
additional investment for the heat recovery is certain to be short, especially in view of the
prospect of continuing increases in oil prices.
Temperature conditioning units on injection molding machines can often be operated by
means of waste heat. However, this application generally requires an especially high heating
medium temperature of at least 60°C. Such temperatures cannot always be achieved simply
by the use of the existing waste heat. A higher condensation temperature is necessary; the
compressor uses more electric energy and the energy efficiency rating of the system drops.
Nevertheless, the use of waste heat can also be very worthwhile in this case. If, for example,
water with a temperature of 60°C is to be provided by the 155 kW cooling unit from our
example above, the output of the system drops to 123 kW. At the same time, the energy
consumption increases to about 67 kW. This results in a total thermal output of 190 kW
which is available for the temperature conditioning units. Operated with electricity, the ratio of
expended energy to generated energy would be 1:1; therefore, the operating costs would be
nearly cut in half in this example.
Severe winters, zero
heating costs. It can be
done – with the Reisner
system, which converts
Despite all the possibilities resulting from the new heat recovery concepts, Reisner never
loses sight of the fact that the core function of their systems is cooling. The main goal here is
always to achieve outstanding energy efficiency ratings. After all, the cooling system is
needed for production anyway and has to be integrated in the production process to the
fullest extent possible. That also has to be considered in amortization calculations, which
should estimate only the additional expense for the waste heat utilization.
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As with any system, it is important that the cooling system with heat recovery also be
adapted fully to operational requirements. This is necessary in order for the Reisner system
to be fully effective: the waste heat is utilized 100 percent and the electric power
consumption of the cooling machine changes only minimally as compared with normal
operation. This guarantees a future-sustainable supply of cold and heat, which will
permanently keep pace with the increasingly stringent climate protection laws and
successfully turn back spiraling operating costs.
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