TKI GmbH
Curiestr. 19 | 09117 Chemnitz
Project description
Motivation
TKI is an engineering office active in the consulting, planning, installation and documentation of telecommunications systems, currently primarily in the fiber optic sector.
Inspired by a functioning solution for sector coupling on a small / private scale and driven by the need to replace the ageing gas heating system built in 1995, the decision was made to switch our engineering office's energy supply to renewable energy sources.
However, it all started earlier - the first PV system was installed during the renovation of the warehouse roof. Somewhat later, the first mild-hybrid vehicle and later a Tesla Model S provided the first experience in the electrification of mobility.
Since then, the path to maximum energy efficiency and CO2 savings has been consistently pursued, and TKI's energy campus is now characterized by the following building blocks.
Building structure
Built in 2006, the new office building with a basement enabled three different office and warehouse locations in the city of Chemnitz to be brought together at the new company headquarters on Curiestraße. The reinforced concrete building designed by the architectural firm Ueberschär.Knoll (Rochlitz) with curtain wall elements and large aluminum/window surfaces already enabled energy-efficient heating through appropriate insulation and the use of panel heating, albeit connected to a large and in parts oversized gas heating system in the existing warehouse building.
Due to the steady increase in the number of employees as a result of the company's continuous growth, Rühlig (Limbach-Oberfrohna) added an extension to the first building in 2018, which was planned by the architectural firm Hauswald (Meissen). The office building with large, multi-functional meeting facilities consistently relies on brick construction and, thanks to the large wall thickness, does not require the additional use of insulating materials. Here too, underfloor heating ensured the possibility of more efficient low-temperature heating.
In 2023, a partial refurbishment of the steel/gas concrete slab warehouse building was carried out, primarily the removal of roller shutters and glass block areas that were no longer required, the replacement of windows and the complete insulation of the building's elevation. At the same time, the reduction of the flow temperatures required for heating and thus the possibility of integration into the low-temperature system was tested over the winter of 2022/2023. Based on the positive test results, the investment decision to replace the heating system was confirmed.
Project details
Geothermal heat generation
Having recognized the need to replace the heating system and on the basis of an energy concept drawn up by eins Energie in Sachsen, the investment decision was made to install a heat pump system on the energy basis of a geothermal borehole field. In discussions with the energy consultancy of the Chemnitz Chamber of Industry and Commerce, the company Lerchner Alternative Heizsysteme (Annaberg-Buchholz) with its highly efficient direct condensation heat pump technology was recommended and, after successful test drilling and proof of the usability of the geothermal probe field, was commissioned with the construction of the new heating system. A total of 12 deep boreholes with a total length of 1,500 m provide the necessary environmental heat for the two cascaded heat pumps, each with an output of 54.8 kW, which ensure a heating load of 70 kW for a total office and storage area of 2,900 m². In the future, the system is to be equipped with additional environmental sources and also used to cool the office buildings. In addition, a cold local heating network and the integration of further environmental sources in the form of ice storage and solar thermal energy are planned for another new office building on the site.
Solar energy generation
The first existing PV system was successively expanded to provide the necessary heating, building and traction current. Three systems with a total of 150 kWp are currently installed on the existing building roofs and further installation of both photovoltaics and solar thermal energy on the roof and façade is also planned for the upcoming extension. A maximum total output of 250 kWp appears possible on the site with the additional façade and roof areas still available. The advantage of the solar generation curve during the course of the day lies in the high potential for self-consumption by all electrical consumers at the commercial site.
Energy storage
Despite the already high proportion of self-consumption, feed-in quantities were determined in the period from March to September, particularly at weekends, which led to the decision to invest in the use of a battery storage system. The decision was made in favor of a scalable system from Tesvolt (Lutherstadt Wittenberg) with a current total storage capacity of 300 kWh and a possible power input and output of 150 kW. The expandability of the system, coupled with the high performance and possible emergency power and stand-alone system functionality, led to the decision in favor of this system.
E-mobility in the company fleet
Based on the initial, positive experiences with partially and fully electric vehicles, the company's fleet was systematically converted to an electrified vehicle fleet. Passenger cars are driving this process, while the replacement of the commercial vehicle fleet is progressing much more slowly. With a total vehicle fleet of currently 77 cars and commercial vehicles, the proportion of partially or fully electric vehicles is already well over half, the majority of which (>80%) are fully electric vehicles. To provide the necessary charging options, the battery storage system controls load management and peak load capping via a total of 20 AC charging stations and a fast charger with two charging points and a maximum output of 150 kW.
Result
Compared to energy consumption in the 2019 survey period, a reduction of almost half of CO2 emissions was achieved across all measures. Despite rising energy consumption, the increase in energy generation and the performance of the heat pump system and battery-powered vehicles have led to more efficient energy use. The use of solar energy generation will therefore continue to be promoted in the future with a focus on maximum self-consumption and an increasing degree of self-sufficiency.
