|Developer||Jari Niskanen, Suomen Lähikauppa Oy|
|Year of construction||1979|
|Surface area||350 m2|
|Heating system||district heating|
|Old ventilation technology||supply air unit, extract with a roof ventilator|
|HVAC design||Sweco Talotekniikka Oy/design director Jussi
Ainamo, design manager Ismo Marin
|Solution||Enervent Pallas HP Aqua with dehumidification
|Design air flow (cooling)||2.0 l/m2 in the sales room|
In this grocery store, Enervent Pallas HP Aqua provides ventilation and heat recovery, as well as the cooling and dehumidification of indoor air. The annual efficiency of heat recovery is over 90%.
Located in the center of Hyvinkää, this grocery store is honored to be a pilot project. It is the first store of the Suomen Lähikauppa grocery chain in which doors were retrofitted to refrigerators. In conjunction with this, the ventilation system of the store was also renovated.
It has been shown that retrofitting doors is one of the most effective ways of affecting the energy consumption of a refrigeration system in a grocery store. It is estimated that it reduces the cooling energy demand to almost one-third of the original demand.
Dehumidification needs attention
However, merely retrofitting doors on the existing refrigeration equipment in an old store would lead to other problems, because the open refrigeration equipment has contributed to the dehumidification and cooling of the indoor air on hot summer days.
In most old stores, like in this one built in 1979, the supply air was only taken directly from outside and heated. Moisture can also enter the store from the door when customers walk in and out and when the store is ventilated.
Without any indoor dehumidification, the conditions are poor. On hot summer days, moisture condenses on cold (usually about +12…+13 °C) refrigeration equipment doors and hides the products behind fogged glasses. At worst, water can drip onto the floor and cause a slipping hazard. If the humidity level remains high for a longer period of time, it will also impair the quality of dry products in the store.
In this Siwa store, the increased moisture load on the indoor air due to the door retrofitting project was tackled by renovating the ventilation system. The old supply air unit was located on the store premises, and one old roof ventilator extracted the air.
– It was a pretty normal solution in the stores of its time, says Ismo Marin, a design manager for Sweco Talotekniikka Oy, the company responsible for the design of the HVAC renovation.
– We also had to find a more energy-efficient and functional ventilation solution, Jari Niskanen continues.
– The old ventilation system could not provide good indoor conditions even before retrofitting the doors to the refrigeration equipment in all climatic conditions.
A versatile solution in one package
Marin says that for this store, the Enervent Pallas HP Aqua unit with dehumidification was an excellent solution, because it enables the recovery of the maximum amount of heat from the indoor air. The unit is equipped with both a mechanical heat recovery system (rotating heat exchanger) and an integrated extract-air-source heat pump. Therefore, its heat recovery capacity is notably higher than that of the traditional heat recovery solutions.
– At times, the temperature of the exhaust air has been below zero, Design Director Jussi Ainamo confirms.
More energy savings are gained by the possibility to run the ventilation in full recirculation mode during the nighttime. Because a CO2 control system is included in the ventilation system, the amount of fresh air is always demand-controlled to maximize energy savings.
The recovered heat is stored in a 500-liter tank. From there, the energy is used for heating the supply air.
During the very hottest days of summer, the heat pump carries out the necessary dehumidification of the supply air by cooling it down to +12…+14 °C. Then the dehumidified air is heated with the after heating coil to a pleasant temperature of +18…+20 °C by using the condensing heat stored in the tank.
The new ventilation system required some new ducts to be fitted. The existing exhaust ducts were left operational but routed via the extract-air-source heat pump to the Pallas HP Aqua unit. It was important to have a ventilation system that provides constant conditions for the entire store area. Moreover, the system had to be as quiet as possible – a requirement that had to be taken into account when sizing the ducts.
– The guys had some serious challenges in fitting the required ducts on and between these low-height structures and the old glulam post-and-beam frame, says the shopkeeper, praising the skills of the installers. The renovation project had to be implemented without closing the shop, and the plan succeeded.
Because the project for retrofitting doors to refrigerators and the ventilation renovation were completed in fall 2013, we have to wait till summer 2014 to see how the supply air dehumidification really works.
– I trust it will work well, Niskanen believes.
So far, the shopkeeper, staff and customers alike have been very satisfied with the new ventilation.
– The store is kept at a constant temperature at all times, and the indoor air quality is also notably better. And the ventilation system is very quiet, Niskanen says and sounds very pleased.