Solar power in cold desert: Ladakh’s new buildings consume more energy; but its unique climatic conditions can rectify this

The cold desert region of Ladakh is characterised by harsh winters, minimal rainfall, and sparse vegetation. For centuries, the region’s remote location and lack of resources prompted residents to adapt ingeniously to the environment, optimising the limited available resources for sustenance. This led to development of many practices, techniques and innovations that are unique to the region and intrinsically embedded into fabric of the local culture.

Traditional Ladakhi architecture is a prime example of this adaptation, using passive solar heating to combat the severe cold. As the region evolved and gained access to grid-based electricity, energy consumption increased, sidelining traditional, climate-appropriate solutions. Given Ladakh’s unique climatic conditions—an altitude of 3,500 metres and over 300 sunny days yearly—it is well positioned to not just revive traditional solar heating practices but also use it to meet its new age resource demands by harnessing solar energy for electricity generation and utilising renewable heating solutions.

Traditional heating in Ladakh

Winters in Ladakh are characterised by extreme cold, with temperatures sometimes reaching as low as -20°C. In the absence of grid-based electricity, Ladakhi architecture evolved by an amalgamation of apt passive heating strategies and material choices to ensure survival through the coldest months.

The resultant buildings were designed to retain heat and featured smaller doors and windows, low ceilings, and thick walls. The kitchen often became the most occupied room, as it served as a central source of warmth due to the cooking activities. Animals were housed on the ground floor, and this arrangement not only provided a buffer from the cold ground but also allowed the animal’s body heat to warm the living spaces above.

The main hall was usually equipped with a Bukhari, a traditional furnace that burns wood or coal. Although many of these practices have gradually diminished over time, the Bukhari is still used in Ladakhi homes today. It provides essential warmth, but its dependence on fossil fuels has a negative impact on both indoor and outdoor air quality, contributing to respiratory issues and environmental pollution, particularly during the harsh winter months when ventilation is limited.

With Ladakh’s connection to the national grid, there has been a noticeable shift in how buildings, including hotels, resorts, and public institutions, manage heating. A team from the Centre for Science and Environment (CSE) observed during field visits that many new constructions are moving away from traditional, climate-suited methods. Instead, these present-day developments increasingly depend on energy-intensive heating systems during winter, significantly contributing to the region’s growing energy consumption. This is evident in Leh, the capital of Ladakh, where winter energy consumption surges across all user categories due to the cold climate, with government buildings consuming nearly five times more energy in winter compared to summer. However, the region also presents unique opportunities to address this rising energy demand.

Ladakh’s unique solar potential

Ladakh enjoys abundant sunlight, with over 300 sunny days annually. According to the data collated by CSE, Leh receives an average annual solar radiation of 6.07 kWh/m²/day (Direct Normal Irradiance). In comparison, most parts of similar cold regions, such as Shimla, receive only 4.42 kWh/m²/day (Reference: https://globalsolaratlas.info/map).

This provides an opportunity to design passively heated buildings, which can effectively warm spaces without relying on active heating methods. This involves orienting most spaces toward the south and incorporating large glazed surfaces to capture maximum sunlight, particularly from the low winter sun, ensuring efficient heat absorption. Meanwhile, the other facades should remain largely glazing-free and well-insulated to minimise heat loss and enhance overall thermal efficiency. As the external temperature decreases at night, the stored heat is released gradually into the interior space, generating convection currents that circulate warm air and maintain a comfortable indoor environment without relying on active heating systems.

The Himalayan Institute of Alternatives Ladakh (HIAL), situated near Leh, has adopted these principles in their buildings and added a few innovations of their own. A key element of the HIAL’s passive solar design is the modified trombe wall on the southern side, with its outer surface painted black to enhance solar absorption. The wall is constructed using concrete blocks with water-filled plastic bottles embedded; the water acts as a thermal battery and maximises the block’s heat absorption capacity. The rest of the building's facades have been made using blocks made with a combination of clay and biomass, such as straw, and this provides the building envelope with the necessary insulation so that it does not transfer back the gained heat.

HIAL conducted a study in January 2021 to assess the effectiveness of these techniques and found that these buildings could achieve temperature ranges of between 20-24°C using only solar energy while the mercury dipped below freezing point outside. In contrast, they reported that a typical room heated with fossil fuels averaged around 12°C.

The CSE team visited other homes in the region that have applied similar principles of design and interviewed the owners. These homes have eliminated active heating, proving the region’s potential for solar-powered heating.

This is the first in a two-part series. Read the second part here