Reliable hot water with SOL•THOR from my-PV
Hot Water for a Boarding School Building in Kenya
The 50 children took cold showers for years. my-PV provided autonomous heating for Kenya’s fragile power grid.
Facts about the project
- Owner
- Project Location
- Photovoltaic Capacity
- Number and Type of Modules
- Thermal Storage Size
- Building Type
- Year of Construction and Floor Area
- Installed my-PV Product
- Heating Element
)
Why a Grid-Connected PV System Was Not Effective
For a boarding school building run by the Sisters of Mercy, a rehabilitation center for street boys, a conversion of the hot water system was planned. Previously, hot water was produced in a 1,000-liter storage tank using a grid-connected photovoltaic system, including a hot water solution from another Austrian company. The problem? The power supply in Nairobi, Kenya, is unreliable. The adequately sized photovoltaic system was intended to generate enough surplus energy to supply hot water, keeping the boiler constantly at 60°C while also covering the electricity demand of the boarding school buildings. However, the system only operated when grid power was available—an unfortunate limitation in East Africa’s volatile power grid. Therefore, a different solution was required to heat water efficiently, sustainably, and reliably. The suitable product also came from Austria.
Personal customer opinion and resumee
Before Reinhard Krall became familiar with the my-PV system, his opinion was clear:
“My view was always that a solar thermal system is preferable for hot water preparation. But as photovoltaic modules keep becoming more affordable and this SOL•THOR from my-PV manages everything so perfectly, photovoltaic heat is now the better option!”
With SOL•THOR, a DC power manager from my-PV, hot water can be produced completely off-grid and independent of the public electricity supply. The device, which is approved for outdoor installation, is connected directly to selected photovoltaic modules and uses the direct current from the modules to power a conventional AC heating element for water heating.
Solar modules with a total output of 4.05 kWp were installed on the two-story boarding school building (ground floor and first floor). The cables run one floor down to the ground level, where the SOL•THOR from my-PV is installed directly next to the 1,000-liter hot water storage tank. Two bathrooms, each with four showers across two floors, are supplied from this tank. Up to 50 children—who would otherwise lack access to such facilities—can now enjoy warm showers.
A conventional heating element purchased from a local market in Nairobi is installed in the hot water tank, making this a somewhat unusual application. The heating element bundle is connected so that one 2 kW element is connected directly, while the other two are connected in series. Since SOL•THOR can operate with a maximum output of 3.6 kW, the series connection ensures compliance with this limit.
How Did an Austrian Photovoltaic Heating Product Reach Nairobi, Kenya?
Nearly 6,000 kilometers separate my-PV’s company location from Nairobi, Kenya. The owner explains how they discovered the solution from Upper Austria: “A former employee of BBM, a procurement organization of MIVA in Stadl-Paura (Austria), suggested that I contact this Austrian manufacturer to look for a solution to our hot water problem. The off-grid solution provides exactly the reliability we could not achieve with a grid-connected PV system due to frequent power outages in Kenya.” Reinhard Krall (left in the picture) worked from 2016 to 2023 as an Austrian development aid worker for Horizont 3000 in the Sisters of Mercy project called Mukuru Promotion Center. He continues to work there and describes his responsibilities: “My tasks include repairs and maintenance, training local staff, supervising new construction, and more—an endlessly interesting and varied job.”
)
How High Is the Hot Water Demand?
The boarding school building typically houses between 40 and 50 boys, along with two supervisors, which pushes the storage tank to its limits. However, this is mainly due to system sizing rather than solar yield from SOL•THOR. Kenya’s location near the equator provides abundant sunshine throughout the year. For comparison, the average daily sunshine duration in Linz, Upper Austria, is 4.6 hours, while Nairobi averages 6.7 hours—almost 50% more. “With economical usage, the hot water supply is sufficient. We use an automatic mixing valve that immediately provides the desired temperature,” explains Reinhard Krall.
The optional backup heating function of SOL•THOR, which could use electricity from the public grid, is not used in this project.
What Are the Advantages of Switching to Off-Grid Photovoltaic Heating?
“A major advantage is independence from grid electricity, especially with frequent power outages in the region. The sun, on the other hand, is reliable and shines intensely year-round here at the equator,” summarizes Reinhard Krall of the Sisters of Mercy. The system consistently generates enough energy throughout the year for the boarding school building. “Another advantage is the perfect control system—there is no overheating as can occur with solar thermal systems,” adds the owner.
What Are the Savings?
The savings cannot be expressed in numbers because the owners had no hot water system at all between 2008 and 2020. “In our case, it simply means improved quality of life through warm bathing water. Energy costs for hot water were never an option,” says Reinhard Krall. In 2020, an Irish donor group funded a hot water system, but it proved incompatible with Kenya’s public electricity grid. After switching in 2025 to off-grid heat generation using SOL•THOR, no monetary savings are achieved, but significant comfort has been added—a privilege that is difficult to quantify financially.
)
)
)
)
)
)
)
)
)
)
SOL•THOR
in use
The DC Power Manager converts solar power directly into heat – efficiently and with minimal loss by using direct current from PV modules to power a heating element.
More infos about SOL•THORMore Reference Projects
)
A resourceful Upper Bavarian benefits from the renovation of his house and implements PV heat as blackout precaution.
Read more...)
The newly built single-family home impresses with environmentally friendly construction and innovative heating technology.
Read more...)
A Polish homeowner is responding to the conditions on the Polish PV market with the AC•THOR 9s.
Read more...