Thermal water system ensures energy-efficient operation of the Zugló district

We have reported on several occasions that the area between Bosnyák Square and Rákos Creek, the Bayer Construct Zrt. group of companies is building Zugló's new city district. As part of the comprehensive development, eight buildings – one residential and seven office buildings – will be constructed on the approximately seven-hectare site. Between them, spacious community and recreational parks and a pedestrian street will serve the comfort and tranquillity of those living and working here. Underground car parks will be built beneath the complex.

The investment will create a new living space that meets today's environmentally conscious and sustainable needs in a prominent part of Zugló. The buildings will be heated with geothermal energy using a modern heat pump system.

The apartments and offices will thus operate at lower overheads than recently occupied buildings, offering tenants or owners a cheaper, more competitive alternative to other offices.

We talked about the details and technical background of the energy system of the Zugló Town Centre with Attila Kántor, the project manager of the geothermal heating system and building services engineering project.

"Our aim is to reduce the carbon emissions of the project, so we were looking for a heating solution that would allow us to replace gas or other heating with green energy. The area has good geothermal potential, so we drilled a thermal well at a depth of almost 1200 metres. We found good water in both volume and temperature - 70-74 degrees Celsius - and we are using this geothermal heating energy to provide heating and domestic hot water for the entire facility."

Our team was also present during the drilling of the thermal well, and we created a spectacular video of the work process.

Geothermal system provides annual heating for 1200 apartment buildings

Attila Kántor went on to explain: "With the nearly 9 megawatt system, we can generate about 65,000 gigajoules/year of heat, which means about 2 million cubic metres of gas per year. That's the annual consumption of 1,200 condominiums. This will provide 100 percent of the buildings' domestic hot water supply, and their heating energy can be provided down to minus 5 degrees Celsius under normal conditions if all buildings are heated at the same time. If we shift these building heaters a little with the right control technology, we can heat the whole season. We have installed state-of-the-art, low-consumption air-to-water heat pumps in the buildings, so that we have back-up energy available in case it gets cold."

The centre of the system, a 450 square metre thermal thermal thermal centre, will be located in building O7. It will house the 140 cubic metre and 60 cubic metre buffer tanks, as well as the entire site's hydraulic units, pump heat exchanger and air-to-water heat pump.

The well and the mechanical equipment, i.e. the heat centre and the thermal pipe network, are located below ground level. The four-pipe system heats the domestic hot water separately and there is a separate building heating circuit. The thermal water circulates between the well and the mechanical room, but not within the plot. Inside the plot, the system runs on plain process water.

The key to recovery is to make optimal use of the water heat gradient

Regarding heat extraction, the project manager said, "We have thermal water process heat exchangers, which extract hot water in a staircase, and if the water still needs it, we extract additional energy with water-to-water heat pumps.

The idea behind thermal water recovery is to maximise the use of water and its temperature. The aim is to maximise the so-called thermal gradient. So, if you take 70 degree water out of the first tank and cool it down to 40 degrees through the heat exchanger, that's still only a 30 degree temperature difference. This is then returned to tank two and from there it is removed by another heat exchanger from 40 degrees to 15 degrees. So we add another 25 degrees, so we can take the energy out of the water with a 55 degree heat step, so we can fully recover the heat energy."

Four water-to-water heat pumps have been installed to maximise heat recovery.

The system uses a quarter of the energy of gas consumption

Sub-thermal centres are installed in buildings to serve the instantaneous heat demand of the buildings. These are parallel systems, the significance of which is that if one building has no heating demand at the moment, the system shuts down and the water flows to all the other buildings, from where it can be extracted.

"We have two systems: heating and hot water. The hot water system works in the same way: what we take heat energy out of, we put it through a domestic hot water heat exchanger, soft water, into the system, so it's not thermal water anymore because it's separated in the same way. There are heat exchangers in each building, and we use them to heat the domestic hot water.

We have tried to use modern, high-quality materials: in the section between the terminal well and the machine house, we use resistant polypropylene pipes with low internal resistance, so we don't need to do as much pumping work to circulate the system, and the transmission line is made of steel pipe. They are all insulated and scalable pipe systems."

In response to our question about the return on investment of the heat pump system compared to other heating systems, Attila Kántor explained that the Zugló City Centre is the most modern office building in Budapest in terms of energy efficiency. Compared to the energy demand of gas consumption, the energy consumption of the system is around 25 percent, i.e. a quarter of the energy consumption.

"Buildings with high energy efficiency will have relatively low heat demand and therefore a good return on investment", he concluded.