Solar energy in northern conditions

Between 2016 and 2019, the number of grid-connected photovoltaic systems in Sweden increased from about 10,000 to just over 44,000, and the power generated from such has nearly quintupled from, 140 MW to 698 MW. Most of these types of facilities are located in southern Sweden, with more than 90% in electricity zones three and four. The same applies to the power generated by them. In project SunCold, RISE is formulating the guidelines on how to install solar panels in the northernmost regions of the country. With the SunCold project, solar energy is being developed to become attractive even in northern latitudes.

– “There is much interest in solar energy even in northern Sweden. However, there was a lack both knowledge and experience in how to use solar energy efficiently at higher latitudes,” explains Malou Petersson, Project Manager for SunCold at RISE.

Within the SunCold project, RISE has produced a handbook with guidelines on how solar panels should be installed in northern conditions. The handbook gives property owners, municipalities and tenant-owner associations a good basis for when different solar systems should be used so that they can make safe decisions about how to invest in solar energy.

– We want to increase interest in using solar energy in the housing sector and the public sector, and can state that the solar energy market in Norrbotten has been strengthened through skills development and collaboration.

Challenging conditions

Producing solar electricity in regions of the far north is challenging. During December and January there is no sunlight at all and even during the rest of the year the conditions are quite different compared to the major markets for solar energy.

– “Because the sun is so low on the horizon, we need to investigate different angles for the positioning of solar panels in order to derive maximum capacity. And, in countries that are very far north, the light from the sun must travel a greater distance through the atmosphere, compared to how it is for countries near the equator for example. The intensity of sun rays is lower at high latitudes. The composition of the sun rays is also affected. Here in Sweden, approximately half of the light we get is diffuse. In other words, it is scattered and comes from all directions. It has neither the intensity nor the glare of direct light. We must therefore optimize solar cells accordingly,” explains Malou Petersson.

Besides the darkness and low height of the sun, snow and cold are two additional factors affecting the production of solar energy in northernmost places. But the impact is not just negative.

– “For silicon solar cells, the cold temperatures actually have a positive impact on their performance. In fact, with a drop in temperature of 25 C, the power they produce increases by 10 %. We’ve verified this at our test facilities, particularly during spring when there is much more daylight, but temperatures are still low,” says Malou Petersson.

Advantages and disadvantages of snow

Snow can also have a positive effect on the energy production from solar cells. When the ground is white and covered in snow, more sunlight is reflected and it can be used for energy production. However, for that to happen, the modules holding solar panels must be designed in a special way. Malou Persson explains:

– “With double-sided modules, we can also make use of the sunlight that is reflected, thereby increasing production. We are studying this very thing at our Solvåg solar farm in Piteå,” she says.

However, snow can also present a variety of problems. If snow accumulates on the modules, it blocks the sun rays resulting in a loss of as much as 20 % of their annual production. The design of the modules must thus take that into consideration.

– "The main rule is to mount solar panels where the solar radiation is great but snow does not accumulate. If the solar cell modules are snow-free already in March, the annual production of solar can increase by about 30 percent", says Mattias Lindh, research engineer at RISE.

Large roofs attractive

Solar modules can break from the weight of snow and ice accumulation. In the worst case, load-bearing roof structures could also get damaged. RISE is also studying the various effects of snow load on solar modules, with the aim of coming up with recommendations on how solar plants should be designed in different snow load zones, then, getting those recommendations implemented in the standards.

– “Snow can damage the modules in several ways. There can be obvious structural damage as well as microcracks that are impossible to see with the naked eye, yet which anyway can have a significant negative impact on production,” says Malou Petersson.

Large low-sloping roofs that are found in industrial buildings and sports halls, for example, have a high risk of snow loads. At the same time, they are attractive surfaces for the installation of solar systems. The knowledge from SunCold is now being further developed in a new project that looks at how such facilities can be adapted to northern conditions.

– "Our hope is that the majority of large industrial roofs will be used for electricity production. We believe this can be possible if we can reduce the snow-related production loss", concludes Malou Petersson.