Figure 1: A conven­tional combined heat and power plant for district heating requires high invest­ments in distri­b­u­tion grids with consid­er­able heat losses over longer distances.

Until now, in many cases indi­vidual large combined heat and power plants have been used outside densely built-up areas to bring hot water to the consumer by district heating supply (Fig. 1). As energy prices and envi­ron­mental stan­dards increase, this method is not always the optimal solu­tion in light of the heat losses, at least for new construc­tions. Instead, the trend is moving towards envi­ron­men­tally friendly, on-site gas heating systems. A deci­sive advan­tage is that the energy loss that neces­sarily occurs over long distances with district heating despite the insu­la­tion of the pipes, is a thing of the past.

The second advan­tage of this proce­dure is the savings in infra­struc­ture. A simple gas pipe can handle a lot of energy compared to much larger district heating pipes with supply and return pipes. In addi­tion, it is easy to see that an insu­lated pipeline is signif­i­cantly more costly than a prac­ti­cally main­te­nance-free natural gas pipe for construc­tion and later during oper­a­tion with main­te­nance and repairs.

Trend towards local heating supply

Figure 2: Compact local on-site heating stations are an ecolog­ical solu­tion for large build­ings as well as for resi­den­tial areas.

There are other factors in favor of the trend away from conven­tional district heating to local heating supply (Fig. 2). From an ecolog­ical stand­point, the mate­rial balance both in construc­tion and in the oper­a­tion of heating with natural gas is signif­i­cantly better than in conven­tional district heating concepts. Espe­cially carbon dioxide emis­sion is rele­vant to the eval­u­a­tion today. Natural gas is the fossil fuel with the smallest CO2 foot­print and as such, it protects the climate.

Further­more, the less addi­tional pipes that have to be laid, the faster projects can be imple­mented. In the case of build­ings like skyscrapers, on-site heating systems can save costs signif­i­cantly and reduce the envi­ron­mental impact. Even in the case of heat supply for resi­den­tial areas, local heating supply can improve the envi­ron­mental balance consid­er­ably. In addi­tion, when new areas are being devel­oped, the local distri­b­u­tion grid can be laid in the construc­tion site quickly and on schedule without having to show too much consid­er­a­tion for existing infra­struc­ture.

Vari­able output improves the oper­ating balance sheet

Today, approx­i­mately 2 MW capacity is required to supply heating water and tap water to build­ings with 50 stories or devel­op­ments with approx­i­mately 100 single-family dwellings. Modern gas firing in premix tech­nology is desir­able because of its homo­ge­neous mixture prepa­ra­tion at lower combus­tion temper­a­tures and complete fuel utiliza­tion. Only very small quan­ti­ties of unburned hydro­car­bons or nitrogen oxides are emitted. In addi­tion, a vari­able heat supply based on a modu­lating burner oper­a­tion also increases the effi­ciency of the entire system. There­fore, precisely in boom cities with strong growth, a modern local heating supply based on natural gas is a genuine alter­na­tive to district heating in terms of the envi­ron­mental foot­print, economic viability, and fast construc­tion progress.

Reducing the cost of instal­la­tion

Figure 3: The new G3G 315 premix blower by ebm-papst Land­shut offers a thermal output that can be modu­lated between 250 and 2,000 kW.

But until now, there has been one disad­van­tage: If larger thermal loads above 1 MW were required for single boilers, there were no suit­able, highly effi­cient gas blowers on the market capable of being modu­lated over a wide range. In order to achieve these capac­i­ties, several boilers had to be installed on site to be oper­ated in cascade. Besides the addi­tional cost of instal­la­tion, this also meant increased main­te­nance costs. With the new G3G 315 premix blower by ebm-papst, a broadly modu­lating gas blower that can be used for heating capac­i­ties up to 2 MW is now avail­able to supply heat to larger units (Fig. 3).

Of course, 2 MW boilers equipped with this blower can also be oper­ated in cascade for even greater thermal loads. This allows the local heating supply of signif­i­cantly larger high-rise complexes, such as those that are being built with increasing frequency, espe­cially in the Asian region (Fig. 4). Thus, the invest­ments and ongoing oper­ating costs of heat supply by natural gas are reduced consid­er­ably.

Good improved and adapted

Figure 4: For large build­ings, a local heating supply on site (e.g. in the base­ment of a high-rise) can save costs signif­i­cantly and reduce the envi­ron­mental impact.

The new gas blower builds upon the many years of expe­ri­ence of the blower special­ists. It is suited for gas condensing units and can also be used in other areas that require a lot of air, such as filtra­tion or process air tech­nology. In the devel­op­ment of this product, the special­ists were able to rely on proved and tested motor compo­nents from their port­folio of blowers and adapt them to the special require­ments of larger heat loads. This allowed the aero­dy­namics of the impeller to be matched opti­mally to the char­ac­ter­is­tics of the motor.

A new motor/electronics config­u­ra­tion now allows rota­tional speeds up to 6,000 rpm. Together, the effi­cient impeller and the opti­mized air duct design of the fan produce a broad turn down ratio of up to 1:8 for the blower. So the blower, as the first in its class, covers an input range from 250 to 2,000 kW in one unit. That is adequate to keep up with even strongly fluc­tu­ating heating require­ments econom­i­cally. Addi­tional gas blower burners are under devel­op­ment for even greater heating capac­i­ties and will soon push the power limit of modu­lating gas premix boilers even higher.

Figure 5: The G3G 315 requires up to 4,300 m³/h (in open-jet oper­a­tion) and builds up a maximum back pres­sure of 6,200 Pa (at full throt­tling).

In addi­tion to the effi­ciency of the burning, easy inte­gra­tion in modern control systems was also a devel­op­ment objec­tive. Thus, a stan­dard­ized inter­face in the motor controller allows the trans­mis­sion of all impor­tant data via a PWM or 0-10 V signal or Modbus RTU, for example. With 380 to 480 VAC and 50/60 Hz three-phase current, the G3G 315 requires up to 4,300 m³/h (in open-jet oper­a­tion) and builds up a maximum back pres­sure of 6,200 Pa (at full throt­tling) (Fig. 5). Here, the flow medium temper­a­ture may be up to 50 °C and the maximum permis­sible motor ambient temper­a­ture is 60 °C. The power consump­tion of the Green­Tech EC motor is up to 6 kW. The housing and fan impeller of the blower measuring 530 x 550 x 365 mm (L x W x D) are made of aluminum. A robust cover protects the motor and the elec­tronics.