Powered by the sun

The sun is a precondition for all life on earth and provides an incredible amount of energy, far more than what is commonly known. Only one hour of solar radiation is enough to meet the global energy consumption for a whole year. Solar energy is being received without any costs and the transformation phase to electricity or heat it is completely eco- and climate neutral. Sunrays hits the user directly and is being delivered without intermediaries. Solar energy is simply quite superior as a carrier of energy!

A common perception is believing we're getting too few hours of sun in Norway. Fact is that we have solar radiation far exceeding our energy consumption throughout the year. If 2 per mille of Norway's land area were covered with solar collectors and solar panels, it'll be equivalent to the entire country's annual energy consumption. 

A typical roof in Norway receives annually 4-5 times more solar energy than the household consumes in a year. In other words, it is quite possible using solar energy to create good conditions for zero-energy or even plus-energy houses!

Solar radiation - Solar collectors and solar panels

Solar radiation hitting the earth's surface can be used for a lot of things. We are talking primarily about solar collectors for heating and hot water and solar panels for production of electricity. Solar radiation may also be used for passive heating and daylight through windows besides this.

HYSS uses solar heat for production of heating, which either passes directly to the storage tank or to increase the efficiency of the heat pump. Operating energy (electricity) needed for the HYSS-system may advantageously be produced with solar cells.

It is common to assume annual solar radiation of 1000 W for 1000 hours per m² horizontal surface in Norway. This implies solar radiation equivalent to 1000 kWh / m² per year. If the surface are facing south and tilted 30º the efficiency will increase approximately by 25%. From southern to northern latitudes along the coast, we substantially have  the same amount of annual solar radiation. In the north there are more solar radiation during the summer and less in the winter compared to the southern part of the country.

The efficiency of thermal collectors is generally between 50-70% for solar heating depending on operating conditionsSolar collectors may contribute with a maximum of 500-700 W/m² producing between 500-700 kWh / m² annually.
The efficiency of silicon solar cells is generally between 15-20% depending whether they are polycrystalline or monocrystalline. Solar cells based on thin film technology generally has slightly lower efficiency (just below 10%). This means that solar cells can contribute with an additional effect of up to 150-200 W / m² producing up to 200 kWh / m² per year depending on technology.


The essence is that solar collectors is about 4 times more area efficient than solar cells. This means that solar heat offers four times higher output and at least four times higher energy conversion per unit area. Still, this doesn't mean that one technology is better than the other. It is important to determine what the energy will be used for and then choose the best qualified technology. If the intention, for instance, is to produce hot water with solar heat, it will be far more cost- and area-effective to choose solar collectors over solar cells. If the solar heat additionally is being used to increase the efficiency of the heat pump, you will achieve extremely high annual efficiency (SCOP) and the season for solar heating will be considerably prolonged. For each part energy (electricity) you add to your heat pump it will return 5-7 times as heating and hot water.



Payback period for solar collectors is normally estimated to 10-15 years depending on the system solution. The power output (number of kWh) by using HYSS will increase because solar heat, in addition to hot water production, is also being used to increase the efficiency of the heat pump. That is why the payback period for "the additional investment" in solar collectors in combination with HYSS is only 5-8 years. The payback period for solar panels are normally between 17-27 years cf. this article in the Norwegian magazine TU.

Read more about HYSS – a heating system powered by the sun.


Cardinal direction and tilt angle

Solar collectors and solar panels can vary considerably both in tilt angle and direction without losing too much efficiency. At Nordic latitudes the deviation in efficiency will be less than 10% if the solar collectors are mounted in directions between southeast (135°) and southwest (225°) with tilt angle between 25° and 65° relative to the horizontal plane.

The efficiency for collectors facing west or east will be less affected if the tilt angle is lower.

Illustration shows that tilt angle of 40° from the horizontal plane facing south will provide the best preconditions. Solar collectors facing east, with the same tilt angle, will decrease in efficiency by approximately 20%. Solar collectors facing east or west, placed vertically, will loose efficiency of approximately 45% compared to optimal placement. These values should not be seen as absolute because it will depend on the latitude.

Best angle of incidence are achieved throughout the year if solar collectors are mounted with 10° lower angle than the operative unit's latitude.  It is however important to realize that optimal placement will have little impact on the overall performance. It’s more important to avoid all kinds of shadow and subsequently ensure a robust installation to create good working conditions (correct flow and low temperatures) in the solar circuit. In the vast majority of cases it is easiest and most cost efficient to follow the roof angle and furthermore aesthetically and architecturally beneficial.

It’s important to remember that the performance of a solar heating system is affected by many factors. An important parameter for good utilization is the operating preconditions. If the solar circuits temperature can be kept low (as in a HYSS-system) the heat loss will be reduced and efficiency will increase.

A point in this context is that HYSS comes with pre-programmed software that makes it possible to manage groups of collectors with different directions to optimize heat production. Solar collector plants with groups facing east and west can be optimized for heat production both morning and evening, i.e. when a household normally has its most intense hot water consumption.

Seasonal storage of solar heat

HYSS generates more solar heat during the summer months than what’s consumed in the house in the period. When the hot water tank is fully warmed by the sun, excess heat is being dumped in the energy storage (usually in a borehole or ground loop). By using continuous recharging from solar energy, Free Energy has initiated a collaboration with ASES (Active Solar Energy Storage) which has developed a patented method for storage of thermal energy. ASES is the most energy efficient way of seasonal storage of solar heat and is constructed under the building's concrete slab for new buildings. The excess heat in the summer, and otherwise throughout the year, are stored in ASES geothermal storage for later use and mostly during the winter months. HYSS in combination with ASES heat storage provides a remarkable low energy consumption and an unmatched annual efficiency, SCOP Combi*, of up to 8!


With ASES geothermal storage and HYSS’ unique control system, the solar heat is utilized maximum throughout the year giving an annual efficiency for heating and hot water (SCOP Combi*) of up to 8. This means for every added kWh of energy to the heat pump you’ll get up to 8 times in return as heating and hot water. The geothermal storage for a new building is constructed under the buildings concrete slab (base plate). If the trenched soil has the proper quality, up to 85% may be recycled for the establishment of the ASES storage and thus reduce costs. Constructing of ASES under the concrete slab (base plate) or foundation, avoids buried tubes in the ground outside the house. This increases the freedom to construct swimming pool, garage, shed or other in the future. It is also possible to place ASES heat storage outside the house, eg. under another unbuilt part of the plot. This alternative is generally more expensive than constructing the heat storage in conjunction with building a new house placing the storage beneath the house.


* SCOP Combi specifies annual efficiency for heating and hot water.


It's always wise to choose HYSS

HYSS utilize solar energy to the maximum. The solar heat is primarily used for direct heating of the storage tank. This will save operating time for the heat pump and reduce the heat output from the borehole or ground loop.

Even at low temperatures solar heat is being utilized to increase water temperature thus significantly improving the heat pump efficiency. Solar collectors in HYSS is being utilized far more hours per year than conventional solar heating systems and increases the efficiency even at low temperatures in the solar circuit. HYSS can also with great advantage, utilize solar energy (solar cells) to run fluid pumps, compressor and other electricity-driven components in the system. It is far more easy to achieve a zero-energy or plus-energy house since the amount of energy are less to handle.

To achieve extremely low energy consumption it is important to identify how the households (or house) energy consumption is allocated. A common household, consisting of 4 persons, heating and hot water represents 80% of the households total energy consumption. The real major savings potential is to enhance the efficiency and reducing energy consumption for heating and hot water.

Allocation of energy consumption in a house
Heating and hot water represents 80% of the energy consumption in a house while remaining household accounts for 20%. Major savings is achieved by reducing the energy consumption for heating and hot water if the objective is to reduce your total energy consumption. To invest in HYSS is an unique opportunity to really cut your energy costs!

Solar collectors are more efficient than solar cells
If solar radiation is 1000W per m² then each m² of solar cells provides 150W power output with 15% efficiency of the solar cells. A solar collector of the same area provides a power output of 600W by the efficiency of 60%. If both units are operating for 1000 hours during one year the solar cells will generate 150 kWh/m² and the solar collectors 600 kWh/m².

The real major advantage of solar heat is accomplished when used in a HYSS-System. Due to the great interchange in the HYSS-system you get 5-7 times in return as heating and hot water for each part supplied energy (electricity) to the heat pump.

Annual efficiency (seasonal performance - SCOP) increases to 5-7 with HYSS
For a conventional heat pump powered by solar cells the utilization from the solar cells will increase with the heat factor of the heat pump, normally between 3-4. This means that you'll get 3-4 times in return for each part supplied energy (electricity) as heating and hot water. Solar heat is utilized by solar collectors in HYSS which are significantly more area efficient than solar panels. Solar heating will additionally provide free hot water and improve the heat pump efficiency meaning for each kWh supplied to the heat pump it generates 5-7 parts of heating and hot water.

Solar collectors becomes an unbeatable investment in this comparison, both technically and economically, in terms of reducing the need for purchased energy for heating and hot water. Solar cells have their advantages naturally by providing electricity to the electrical components in HYSS. By utilizing both solar and solar heat this becomes the ultimate combination!

HYSS makes it easier to acheive the standard of a zero-energy house
By using HYSS the need for added energy for heating and hot water supply is reduced. With solar cells it also becomes easier to manage the supply of electricity. Through combination of HYSS and solar electricity, the possibility to create a self-sufficient house increases with clean renewable and free flowing energy.

Sizing of solar energy facility for zero-energy house (new building)
Household electricity: 4000 kWh/year
Heating and hot water: 9000 kWh/year
Solar panels per 1000 kWh: 7m2
Following area is required for a solar energy facility to acheive 0 balance:
Without geothermal heat pump (only solar panels): 91m2 solar cells
Geothermal heat pump with 8m² thermal solar collectors (HYSS): 36m2 solar cells

Solar radiation can be transformed into heat or electricity or naturally both. The greatest potential for reducing energy costs is to utilize solar heating because the largest part of the energy consumption in a household is heating and hot water supply.