© Fraunhofer

Mod­u­lar façade with inte­grat­ed plant tech­nol­o­gy sup­plies build­ings with renew­able energy

The ren­o­va­tion rate in the build­ing sec­tor is still too low to achieve the ener­gy turn­around with­in the time­frame envis­aged by the Ger­man gov­ern­ment. One step in this direc­tion may be a greater degree of pre­fab­ri­ca­tion of the com­po­nents. Researchers from Fraun­hofer IBP and Fraun­hofer IEE are devel­op­ing a façade mod­ule that inte­grates tech­ni­cal build­ing equip­ment (TGA) and sup­plies it with renew­able ener­gy to heat, cool and ven­ti­late the rooms behind it. This is made pos­si­ble by a PV sys­tem inte­grat­ed into the mod­ule facade for ener­gy gen­er­a­tion, a micro heat pump for heat­ing and cool­ing, and a decen­tral­ized ven­ti­la­tion unit with heat recovery.

Build­ings account for a sig­nif­i­cant share of total ener­gy demand and green­house gas emis­sions in Ger­many. Ener­gy-opti­mized build­ings, intel­li­gent con­trol and net­work­ing, and an eco­nom­i­cal and cli­mate-friend­ly ener­gy sup­ply for homes are there­fore cen­tral com­po­nents of a suc­cess­ful ener­gy and heat tran­si­tion. Pho­to­voltaics (PV) will play a sig­nif­i­cant role in a sus­tain­able ener­gy future — for exam­ple, in the ren­o­va­tion of exist­ing facades, but also when it comes to reduc­ing the ener­gy demand and con­sump­tion of new buildings.

Research teams at Fraun­hofer IBP and Fraun­hofer IEE are cur­rent­ly devel­op­ing a so-called EE-mod­ule façade (renew­able ener­gy mod­ule façade), which sup­plies the build­ing with envi­ron­men­tal­ly friend­ly elec­tric­i­ty and thus heats, cools and ven­ti­lates the rooms. At the heart of the mod­ule is a PV sys­tem com­bined with a heat pump as a high­ly effi­cient heat and cold gen­er­a­tor, as well as a decen­tral­ized ven­ti­la­tion unit with heat recov­ery. All the nec­es­sary tech­ni­cal com­po­nents are accom­mo­dat­ed in the EE mod­ule façade ele­ment, thus achiev­ing a high degree of pre­fab­ri­ca­tion. The Ger­man Fed­er­al Min­istry for Eco­nom­ic Affairs and Ener­gy BMWi is fund­ing the joint research project. The project part­ners are Imple­nia Fas­saden­tech­nik GmbH as the design­er of the EE mod­u­lar façade. The com­pa­ny Lare GmbH Luft- und Käl­tetech­nik devel­ops the heat pump, and LTG AG com­ple­ments the area of decen­tral­ized ventilation.

Min­i­mal­ly inva­sive facade renovation

The aim of the research project is to devel­op a cost-effec­tive mod­u­lar ren­o­va­tion and new con­struc­tion façade, where­by the ren­o­va­tion is to be min­i­mal­ly inva­sive — as is the case with many oper­a­tions in med­i­cine. “We are not ren­o­vat­ing the entire build­ing, just the facade. In the future, the old facade will be replaced by new indus­tri­al­ly pre­fab­ri­cat­ed mod­ules with inte­grat­ed plant tech­nol­o­gy, which will thus make it mul­ti­func­tion­al and adapt it to the new ener­gy stan­dards,” explains project man­ag­er and sci­en­tist at Fraun­hofer IEE Jan Kaiser. “The entire heating/cooling and ven­ti­la­tion tech­nol­o­gy for the office space behind it will be inte­grat­ed into the facade.”

Since the mod­ules can be pre­fab­ri­cat­ed, they can be pro­duced off the shelf. This gives plan­ners and investors a high degree of cost cer­tain­ty and a clear­ly defined cost frame­work. The replace­ment takes place in just a few hours. Since the heat­ing and ven­ti­la­tion tech­nol­o­gy is already inte­grat­ed, no new pipes need to be laid inside the build­ing. The facade only needs to have a pow­er con­nec­tion to be able to air con­di­tion and ven­ti­late the rooms even in times with­out PV pow­er. The instal­la­tion and coor­di­na­tion effort at the con­struc­tion site is reduced. Ide­al­ly, the users of the rooms do not have to move out sep­a­rate­ly dur­ing the refurbishment.

The EE mod­u­lar façade is par­tic­u­lar­ly suit­able for office, admin­is­tra­tive build­ings and schools built in skele­ton con­struc­tion — a con­struc­tion method that was com­mon in the 50s, 60s and 70s. Instead of load-bear­ing walls, rein­forced con­crete columns hold the floor slabs. Dur­ing the ren­o­va­tion, the old façade ele­ments are removed and the new type of floor-to-ceil­ing mod­ules are hung in front of the build­ing struc­ture. A sin­gle tech­ni­cal unit of the EE mod­ule facade is 1.25 m wide and 30 cm deep. Each unit can sup­ply a room of approx. 24 m².

Mod­u­lar façade as an ener­gy envelope

The built-in PV sys­tem gen­er­ates the ener­gy and sup­plies pow­er to the sys­tem com­po­nents such as the heat pump. This func­tions as a heat and cold gen­er­a­tor at the same time. It is the defin­ing com­po­nent of the tech­ni­cal unit of the EE mod­ule façade and is char­ac­ter­ized by intel­li­gent con­trol of the ener­gy flows. From one unit of elec­tric­i­ty, it can pro­duce three to four units of heat. Via a fan coil unit mount­ed in the air gap behind the PV ele­ment, it extracts the heat from the out­side air and emits it as heat­ing heat to the (office) room behind it, also via a fan coil unit. If it needs to cool instead of heat, the cycle is reversed, extract­ing heat from the indoor air and dis­si­pat­ing it to the out­door air.

An inte­grat­ed decen­tral­ized ven­ti­la­tion tech­nol­o­gy unit con­trols the air exchange and heat recov­ery. By selec­tive­ly inter­con­nect­ing air dampers, only one fan is required, which min­i­mizes pow­er con­sump­tion. The sys­tem devel­oped by Fa. LTG, the ven­ti­la­tion unit alter­nates cycli­cal­ly between sup­ply and extract air oper­a­tion and thus per­forms a kind of breath­ing. In addi­tion, vac­u­um insu­la­tion ele­ments pro­vide ther­mal protection.

“The new EE mod­u­lar façade offers pre­cise­ly coor­di­nat­ed ther­mal and solar pro­tec­tion while at the same time keep­ing ener­gy require­ments low and pro­vid­ing a high lev­el of user com­fort,” empha­sizes Michael Eberl, a sci­en­tist at Fraun­hofer IBP and a col­league of Jan Kaiser in the project. About 25 to 30 per­cent of all office build­ings were built in skele­ton con­struc­tion from 1950 to about 1990. They have a con­sump­tion of 3200 gigawatt hours (GWh) per year. “With our RE mod­ule façade, con­sump­tion can be reduced to 600 GWh. The low ren­o­va­tion rate of one per­cent per year could also be increased by the high degree of pre­fab­ri­ca­tion,” says Kaiser.

Tests in the exper­i­men­tal facil­i­ty for ener­gy and indoor cli­mate stud­ies (VERU) of Fraun­hofer IBP in Holzkirchen

Cur­rent­ly, the project part­ners are test­ing the demon­stra­tor of the EE mod­ule façade on the south front of the VERU build­ing, includ­ing a test room behind it. Both the demon­stra­tor and the test room are equipped with exten­sive mea­sure­ment tech­nol­o­gy. In addi­tion, time-depen­dent con­trolled inter­nal heat and humid­i­ty sources — which sim­u­late “users” in the rooms — are installed to demon­strate the func­tion­al­i­ty in a real office envi­ron­ment. Among oth­er things, para­me­ters such as air tem­per­a­ture, air humid­i­ty and air veloc­i­ty at dif­fer­ent heights as well as the illu­mi­nance are deter­mined — para­me­ters that are rel­e­vant for the com­fort in the room. The elec­tri­cal con­sump­tion of the indi­vid­ual com­po­nents of the tech­ni­cal unit of the EE mod­ule façade is record­ed, as are the yields of the PV ele­ment, in order to cal­cu­late an ener­gy bal­ance. The inter­ac­tion of all com­po­nents already works very well, indi­vid­ual com­po­nents are cur­rent­ly still being optimized.