Energy independence. Synergy between heating, photovoltaics, and graywater heat recovery at the hotel

This configuration--designed by Piotr Leszek and implemented by EOD--is a prime example of intelligent energy priority control (known as peak management).

1. Introduction and Property Profile

The Sunny Hill Hotel in Karpacz is a high-end facility located in the challenging mountain climate of the Karkonosze Mountains. Due to the harsh local conditions, the temperature of the potable water supplying the building averages only 8 ?C. The property is characterized by a high demand for thermal energy (both for space heating and for domestic hot water). To ensure the highest standard of comfort for guests, the building operates a 24-hour, temperature-controlled circulation system. The entire system has been in operation since 2013, representing over 13 years of continuous, stable, and trouble-free operation. The system was designed by Piotr Leszek, and EOD served as the main contractor for the installation. Water consumption during the period under review amounted to 1,106.9 m3 (1,106,900 liters), and current electricity costs are 1.10 z? (~0.26 EUR) per kWh.

2. An Advanced Technological Concept (Synergy of the Four Pillars)

The installation design created by Piotr Leszek in 2013 was unique and groundbreaking. The technical solutions employed and the approach to creating synergy among renewable energy systems were well ahead of the planning practices of the time and the market standards applicable to hotel facilities. The system is based on the complete integration of heat generation, waste heat recovery, and electricity generation.

The first pillar is a dual-function heat source in the form of a 35-kW brine/water heat pump with an average annual coefficient of performance (COP) of 4.5, which extracts energy from the ground via five geothermal probes, each 100 meters long. This unit fulfills two functions: it heats the entire hotel building and supplies energy for domestic hot water. The second pillar is the FriWa fresh water module. Domestic hot water is not stored in conventional, large storage tanks--instead, the FriWa module heats it on a flow-through basis using an efficient plate heat exchanger, thereby eliminating the risk of Legionella bacteria growth. The third pillar is heat recovery from graywater using the Showersave system. This system utilizes vertical heat exchangers (DWHR) that are integrated directly into the downpipes through which shower water is drained from the hotel bathrooms. The units installed in 2013 have an efficiency of 47% and have impressed with their superior build quality--operating maintenance-free and trouble-free for over a dozen years. They form the technological foundation of the system; the latest Showersave models currently in production raise the bar even higher, achieving an efficiency of over 70%. The fourth pillar is on-site electricity generation and peak load management via a 10 kWp photovoltaic system. The PV system generates approximately 10,000 kWh of free electricity annually and works closely with the intelligent Energy Priority Management System (EMS). This makes it possible to automatically activate intensive heating and heat storage processes during periods of maximum solar power generation, thereby minimizing the cost of purchasing electricity from the grid.

3. Engineering Challenge: DHW Priority versus Heating Stability

In conventional systems based on a single heat pump, simultaneously heating the building and providing domestic hot water creates a serious technical conflict. During periods of high hot water demand (e.g., during morning or evening shower peaks), the heat pump must switch to "DHW priority" mode and completely shut off the building's heating. Furthermore, the continuous operation of the temperature circulation system constantly cools the buffer tank. In a 35-kW system, this could lead to underheated hotel rooms during cold snaps in Karpacz.

The combination of the Showersave and FriWa module systems has completely eliminated this risk. First, Showersave increases the inlet temperature--the hot water flowing into the drain transfers its energy and heats the cold drinking water from 8 ?C to a significantly higher temperature. This directly reduces the load on the heat pump, as the FriWa module requires significantly less energy from the buffer tank to heat the water to the target temperature of 50 ?C. As a result, the operating time in hot water priority mode is reduced. A 35-kW heat pump heats the water virtually instantly and can return almost immediately to its primary task--heating the hotel building.

4. Data Analysis and Energy/Cost Balance for Domestic Hot Water (DHW)

In a theoretical scenario (with no losses and no use of renewable energy technology, at a COP of 1.0), heating 1,106,900 liters of water from 8 ?C to 50 ?C (temperature difference of 42 ?C) using conventional electric heating elements would result in a theoretical heat demand of 54,057.31 kWh. This would correspond to a minimum theoretical cost of 59,463.04 PLN (~13,893.23 EUR).

In the actual scenario at the Sunny Hill Hotel, real-world losses due to the 24/7 temperature circulation system were also taken into account. If the system had not been equipped with the Showersave wastewater heat recovery system, the system's total energy requirement (net heat + circulation losses) would originally have amounted to up to 115,544.32 kWh of heat. However, thanks to the use of vertical Showersave heat exchangers with an efficiency of 47%, 35,256.00 kWh of energy was recovered directly from the outgoing graywater. As a result, the actual energy demand that had to be met by the heat source (buffer tank) dropped to 80,288.32 kWh of heat.

Taking electricity consumption and costs into account--including the heat pump (COP 4.5) and PV system--the heat generation costs were reduced to 0.2444 z? (~0.057 EUR) per kWh. The heat pump's total electricity consumption for domestic hot water (DHW) amounted to 17,841.85 kWh of electricity. Thanks to the 10-kWp photovoltaic system, which provided 5,500 kWh of electricity directly for operating the heat pump through self-consumption, electricity procurement from the grid dropped dramatically to 12,341.85 kWh. The final bill for grid electricity used for DHW totaled 13,576.04 PLN (~3,171.97 EUR). This means that the actual cost of heating 1 liter of water was 0.0122 z? (~0.0028 EUR) per liter--or just 1.22 groszy [~0.28 eurocents] per liter of hot water from the tap.

5. Summary of the Economic Benefits for the Hotel

Comparing the performance of the domestic hot water system in a standard configuration without heat recovery (COP 1.0, taking into account actual circulation losses at the primary level of 115,544,32 kWh) with the complete system at the Sunny Hill Hotel (heat pump COP 4.5 + FriWa + Showersave + 10 kWp PV) at an electricity price of 1.10 z? (~0.26 EUR) per kWh, the following results are obtained:

Electricity consumption from the grid: Reduction from 115,544.32 kWh in the conventional system to just 12,341.85 kWh at the Sunny Hill Hotel.

Total cost per 1 kWh of heat: In the baseline scenario, 1.10 z? (~0.26 EUR); in the integrated system, this figure is reduced--taking into account the free energy from wastewater heat recovery and solar power--to 0.1175 z? (~0.027 EUR).

Total electricity costs for the hotel: In the standard system, they would have amounted to 127,098.75 z? (~29,695.97 EUR), while they actually totaled only 13,576.04 z? (~3,171.97 EUR).

Cost of heating 1 liter of water: Decreased from 11.48 groszy (~2.68 eurocents) to just 1.22 groszy (~0.28 eurocents).

Savings Achieved: The entire system resulted in an actual cost reduction of 113,522.71 z? (~26,524.00 EUR), corresponding to a total savings in operating costs of 89.3%.

6. Summary and Conclusions

The implementation of the system led to four key conclusions. First, thermal comfort in the building was fully maintained. The use of vertical Showersave heat exchangers and the FriWa module immediately prevented the heat pump from having to constantly shut down the building's heating function in favor of hot water production. The reduction in hot water delivery time made it possible to maintain the ideal temperature in the guest rooms even during the harsh winters in the Giant Mountains.

Second, the integration proved to be a resounding financial success--at current rates, the absence of the implemented solutions (heat recovery and renewable energy) combined with the actual circulation losses would have resulted in expenses of approximately 127,000 PLN (~29,700 EUR) for hot water alone, whereas these costs now amount to only about 13,500 z? (~3,170 EUR).

Third, Showersave's uncompromising quality has been confirmed. The system's trouble-free operation since 2013 positions the graywater heat recovery technology used by Showersave as one of the most reliable components of renewable energy systems. Over thirteen years of maintenance-free operation, combined with the development of new models with an efficiency of over 70%, opens up tangible savings potential for further investments in the HoReCa sector. Fourth, the investment has proven to be timeless.

The integration of a heat pump, photovoltaic modules, a fresh water module, and wastewater heat recovery ensures low operating costs, resilience to energy crises, and a high degree of independence for commercial properties. The installations designed by Piotr Leszek in 2013 represented a rare example of technological foresight at the time and set modern development trends for the entire hospitality sector.

All of the above data is based on continuous monitoring of heat meters and over 13 years of trouble-free operation of the systems installed by EOD Technologies Sp. z o.o., based on a design by Piotr Leszek.

Designed by Piotr Leszek (p.leszek@eod-technologies). Implemented by EOD Sp. z o.o. in 2013. www.eod-technologies.eu

EOD Technologies Sp.z o.o
u.Mickiewicz 22
58-500 Jelenia Gora
Polen

https://www.eod-technologies.eu

Herr Michael Ilgner
0048 -(0) 732 351985

m.ilgner@eod-technologies.eu

The Polish company EOD Technologies Sp. z o.o. (www.eod-technologies.eu) is a subsidiary of the Dutch company Dutch Intraco Holding B.V., which specializes in the custom development and turnkey construction of client-specific power generation plants, energy storage solutions, and energy-efficient measures of various capacities and technologies.
In addition, we offer comprehensive installation and maintenance services, including the design and implementation of holistic energy solutions, the implementation of energy-efficiency measures for commercial and industrial sectors, and the optimization of energy consumption.

This release was published on openPR.