Load on the compressor increases due to solar heat entering through roof top and side walls. This becomes very significant in India, during summer months. Any reduction in this heat load will save good amount of electric power. Also, the life of compressor will improve and down times will reduce to some extent.
Many approaches have been suggested for reducing heat entering through the rooftop. Ideas such as Cool roof coating, White tiles, Metal roofs, Green Roofs, Solar Panels, Sprinklers, Balloon based shading of roof etc. (For more details, please see July 2024 issue of Cooling India)
Even though so many ideas have been proposed, the implementation has been limited. There are many reasons for these ideas not being implemented on a wider scale. Some of the reasons are:
- Management is usually reluctant to make any structural changes to the building.
- Any construction or changes to the roof top can damage the water proofing, which will result in water leakage in rainy season.
- Increased human activities inside the cold storage building, increases load on the compressor. Thus, defeating the very purpose.
- Management is reluctant to make additional investment, when loan payback is in progress.
- Extra maintenance/ repair expenses.
- These extra activities may be a distraction from the basic cold storage management activities.
The proposed method to reduce heat entering through the walls
Heat entering through the side walls can be easily stopped by planting trees around the cold storage building. However, this is usually not done because of several reasons such as:
- The roots of big trees may damage the building foundation.
- The movement of trucks and other vehicles may get restricted when the trees grow big.
- If in future, any expansion is to be done, permission for felling the trees may not be easy to obtain.
- Keeping the premises clean from dry leaves, branches etc, may increase maintenance cost.
A new method is proposed here. In this method, tall potted plants are used to stop sunlight falling on the side walls of the cold storage units. While proposing this method, care has been taken to avoid all the disadvantages of the roof top approach listed above. Further, the disadvantages of planting large trees, as listed above, are also not there in the proposed method.
In this method, potted tall plants are arranged in front of the wall(s) of the cold storage unit. In order to cover the height of walls, pots are arranged in three levels. For this purpose, a stepped stand with wheels is fabricated as shown in Fig. 1. This stand can be made using stainless steel pipes and angles.
Figure 2 shows the side view of the stand with potted plants arranged on each step. About 2 feet tall white colour (ceramic) pots are selected. The plant is about 5 feet tall.
Cooling action takes place in following three ways:
- Plants block sunlight falling on the wall.
- Drip irrigation for plants and the greenery keeps air surrounding the building cool.
- White ceramic pots and stainless-steel stand reflect sunlight away from the building.
Advantages of the proposed method:
- The stands are kept about 1 ft away from the building. Hence, there is no structural change needed to the building. Also, there is no danger to the building structure.
- Installation and maintenance are done from outside of building. There is no need for maintenance staff to enter the building.
- Easy and quick installation possible. Also, removing is equally simple and quick.
- Due to seasonal changes, when sunlight shifts to other walls, stands could be moved there quickly.
- Give good aesthetic look to the premises.
- This work can be outsourced to a local nursery with single point of contact. Which can reduce initial investment. Monthly payment can be done easily from the savings accrued from reduced electricity bill.
Plant selection
Plant selection is based on two factors. It should produce good shade and need very less maintenance. After doing an exhaustive search, the popular Morpanthki or Thula plant (Arbor-vitae) is selected. A closeup view of this plant is shown in Fig. 3. Figure 4 shows the potted plant. Usually, these plants grow to 5 or 6 feet in height when planted in a pot. So, the total height will be about 7 feet.
This plant offers following advantages:
- It is an ornamental plant which remains green throughout the year.
- It has dense branches which give good shadow and good landscaping.
- It is a sun loving plant and grows well in variety of climatic conditions.
- It grows in tall conical shape which makes maintenance easy.
- It is a low maintenance plant and does not need much care to grow.
- It generates very less dry bio-mass. Hence, easy to keep the premises clean and tidy.
- It purifies air and absorbs noise.
For these reasons, Morpankhi is a fairly good choice for this application. Figure 5 shows the potted Morpankhi plants arranged along the walls. Stands are arranged where ever there is gap between two docking doors.
Vijay Deshpande has done PhD from IIT Kanpur in Electrical Engineering. He has worked in several companies in India. He worked as Technology Specialist and retired from Honeywell India. His current interests include working on cost effective Cooling Techniques and also on Solar Photovoltaic Systems. He has published several research papers in International Journals and published many articles in leading magazines
