ContactContact and location
SECMOL - Students' Educational and Cultural Movement of Ladakh
Solar Energy

Renewable energy in High Cold Deserts

Film 20 min. about a course at SECMOL in 2013 called the Apprenticeship on Sustainable Sanitation, Passive Solar Design, and Earth Building Construction

Video 2 min. SECMOL founder Sonam Wangchuk talking about solar energy.

Video 1 min. in Korean about SECMOL's solar cooker by a volunteer in 2011.

Ladakh is the northernmost region in the Jammu & Kashmir State of India. It can be called a 'Trans-Himalayan high altitude desert' with minimum temperature in winters -20°C to -35° and hardly any rainfall. Leh, the capital, is at 11,500 feet (3500m).

The cold climate of Ladakh demands heating, but lack of rainfall makes trees and firewood scarce. However, average 300 sunny days per year make this region especially suited for solar energy.

Ladakh panorama

Since 1994 SECMOL has developed solar heated buildings and used other forms of solar energy to make its campus at Phey self-reliant.


Our campus is almost completely solar powered. We use solar electricity for all our electrical and pumping needs. The campus has two solar cookers and solar water heaters for bathing. Most noteworthy are the campus buildings, which depend on passive solar heating to keep warm even in the coldest months of winter.

Solar panels

Four arrays of 16-24 panels each generate electricity for lighting, computers and TV. On sunny days we can even use carpentry and soldering tools. The power is stored in solar batteries for nights and cloudy days.

Solar Panels


Solar cookers

Our kitchen uses two concentrating reflector-type solar cookers to cook much of our food directly on the sun's rays. They were assembled in 1997 by a group including SECMOL students at a local workshop under Swiss direction.

Solar Cookers

The cooker has a large parabolic reflector made of household mirrors, that focuses the rays of the sun to a secondary reflector under the pots inside the kitchen. This design gives energy equal to a large gas burner, and saves a lot of money while preserving the environment.

Solar Cookers

Solar cooker.

SECMOL solar water heater

For bathing we designed a very low cost solar water heater from basic materials easily available.

A great advantage of this design over expensive commercial models is that it has no pipes inside that can freeze and break, so it can be used all winter without draining. Since it is basically a large shallow tray, if it freezes overnight, nothing breaks, and in the sunny morning it simply melts and starts warming up again.

Low cost solar water heater


SECMOL solar water heater

a. Aluminium sheet painted black, black plastic or cement with black tiles.
b. Greenhouse plastic to cover it.
c. Frame made of mud bricks or wood.
d. A common toilet-tank valve if desired

The bottom is a black tray that can hold two inches (5 cm) of water. It must be black to absorb the sun's light and convert it to heat, and can be made either of sheet metal bent up at the sides to form a tray, or black pond-liner plastic (tough and UV resistant).

We find that 3 feet (1 m) is a good maximum width to allow maintenance without walking on the base, and the tray can be as long as you have space and materials. Our are about 18 feet (5 m) long.

It is covered with a small plastic greenhouse. In the winter the one on the bathroom roof is inside an additional plastic greenhouse.

We fill it with water in the morning, and by 12 noon it makes 100 litres of 45°C water. Shallower will get hotter faster. A common toilet tank valve on the inlet pipe prevents overflow by automatically letting cold water in when warm water is drawn out, and cutting the supply when the water level reaches the desired height.

SECMOL buildings and passive solar design

SECMOL buildings are heated without emitting CO2, burning anything like firewood or gas, or electric heaters. The buildings are designed to absorb heat from the sun and to store it for as long as possible. This 'passive solar design,' is distinct from active designs which use circulating water pipes, air blowers, or moving parts. With passive solar design the SECMOL buildings have stayed warm and not needed any external heating in the last 15 years — even when the minimum outside temperatures falls to -25°C.

Running solely on passive solar heating, the temperature in the main building at SECMOL Campus has been:

Average evening temperature in winter: +14°C
Minimum in a normal winter: +10°C
Minimum observed in 11 years: +7°C

In the main building at Phey Campus the stair wells have geranium and other plants blooming and flourishing even in January when the minimum outside temperature is -25°C.

The important features to keep the buildings warm are:

  • South facing windows, as the sun stays low in the southern sky in winter.
  • Greenhouses attached the south side for winter.
  • Greenhouses are removed in springtime to prevent overheating.
  • Skylights are covered with glass or clear plastic to trap warm air.
  • Thick earthen walls and floors to store collected heat (thermal mass).
  • Insulation in ceilings, outer walls and under the floor.
  • Low cost local materials like earth and stones.
  • Natural lighting so electricity is not needed for lighting in the daytime.

Windows and greenhouses to the south

In winter, huge plastic sheets come down and make a big greenhouse which works as a solar collector for the building. The plastic stays rolled up away in summer to prevent overheating. This ultraviolet stabilised plastic is commonly used for agricultural greenhouses in Ladakh.

A bonus feature of the plastic covering is that they make excellent spaces to grow vegetables and flowers in the Ladakhi winter.

Growing of vegetables

Thermal mass in walls and floors

We build our buildings three feet (1 m) or more below ground on the north side. The building benefits from the stability of earth’s temperature at that depth, which is relatively warm in winter and cool in summer. It also helps us get the building material — earth — right on site. The earth we dig out ultimately becomes the walls of the building.

The walls are build of rammed earth, a most eco-friendly method as the building material comes right from the site and is not transported hundreds of miles, and when construction is finished, there is no debris to be thrown away: no addition, no subtraction. Earth buildings are the warmest in winter and coolest in summer, and also moderate the humidity of the building.

The technique of rammed earth consists of casting huge bricks in place, in a frame made of planks. Sand and clay are mixed in the right amounts to get a very strong constitution. It is then packed in the frames and rammed with pounders.

Rammed earth wall
The thick earth walls are not just structural (to take load) but also have an essential function as the heat bank (thermal mass). They absorb the excess solar heat during the day and release it to the room at night. The same properties also keep rammed earth buildings cool in summer.

Rammed earth is an ancient technique used in monasteries, castles and forts around Ladakh. These structures have survived, unprotected and exposed to the elements, for hundreds of years.

Ancient fort at Basgo

While we resurrected this method in Ladakh, we were pleasantly surprised to learn that there is a resurgence of this technique in many western countries in Europe, North America, and Australia.

Insulation in ceilings, outer walls and floor

Insulation retainw the heat collected during the day, but it does not have to be expensive modern materials. The wood waste generated during the construction is filled in the ceiling to stop heat loss through the roof.

Insulation of the roof

Insulation below the floor is also important. Layers of various sizes of rocks create insulating air-pockets between the rocks. A top layer of gravel and cement acts as a heat bank.

Sometimes the top layer of the floor is slates from nearby mountains. This reduces the use of cement, and the slates also become a thermal mass or heat bank as they are now cut off thermally from the cold ground.

Slates on the floor

This kind of floor absorbs the excess heat during the day and releases it during the night. Otherwise floors can be an area of big heat loss.

The outer walls are insulated by a jacket wall outside the main structural wall. The six inch gap between the two walls is filled with low cost insulation: saw dust, wood shavings or sometimes paper and plastic garbage like bottles and bags. Sometimes we have also used cow dung as an insulating plaster. Mixed with the right amount of earth and clay, it makes a strong and thermally effective plaster.

Dung plaster for walls

If comparing 'thermal conductivity' (insulation property) of common Ladakhi building materials, you find that mud is the best:

1 ft mud wall = 2 ft concrete = 4 ft stone = 1.5 inch of saw dust. = 1 inch of Thermocol, rockwool etc.


Natural lighting: the sun

Windows and skylights ensure that no place in the building needs electric lights in the day.

Library lightwell

Light well in the main building on Phey Campus.

Sheyson Solar Earthworks

A commercial, income-generating section, Sheyson Solar Earthworks ran from 200 till 2008 to build solar buildings on turn-key contract for private homes, the government, NGOs, and the army. The profits from Shesyon Solar Earthworks supported educational reform, environmental awareness activities etc. Starting in 2009 Shesyon Solar Earthworks is on hold.

Sheyson projects

Sheyson completed many solar projects around Ladakh.

The Army Goodwill Headquarters in Leh, 2005:

Army Goodwill Headqarters animation

View animation:

(requires Macromedia Flash player 8)

Low quality (for modem connections) View »
High quality (for broadband connections) View »

Contact Sheyson Solar Earthworks.