The sun it the most reliable renewable energy source we have, but how can we use it in a cost effective way ?? And what is solar energy ?? and is solar energy cost effective ??
When you google or read about solar energy it seems that the majority agree, that solar energy is coming from solar panels or solar PV cells, producing electricity.
If you analyse the costs of this solar electricity you will soon find out, that it is far more expensive than electricity from other renewable sources connected to the grid, e.g. large wind turbines. However for off-grid installations providing the consumers with 12 V electricity for LED lighting and low energy electronics they are unique. So the answer today is both a no and a yes. In the future we may hope for a double yes.
But what about solar hot water panels?
Hot water panels are standing in the shadow of the solar PV, almost forgotten, and mainly known as solar hot water panels for single family houses. These small panels on the roofs are not cost effective in urban areas in which we can produce the hot water much cheaper with surplys heat and renewables via district heating. However, they are very successfull on the roofs of single family houses in e.g. Southern Europe and China. So also here the answer depends on the conditions.
The newest development is however large-scale solar water heating plants based on large efficient panels. The solar energy provided as hot water up to 90 dgr.C from such plants, typically larger than 10,000 m2 of panels is very cost effective and competitive against oil at world market prices. The plants are booming in Denmark to supply district heating networks, but almost unknown in most other countries. In Chile the first very large plant for the mininig industry is under construction.
What makes them cost effective ?
The secret seems to be that they are optimized with the aim to be competitive. Therefore they are simple and efficient and the benefit from the large scale effects. The larger fields, the more cost effective up to around 20,000 m2. Also the heat storages, which level out the solar heat during some days are much more efficient and cost effective in large scale. The only precondition for using these cost effective panels is that you have a corresponding large demand for hot water in the summer months, which you have in district heating systems and e.g. in some mining industries.
One more advantage with the large solar heating plants is that they are monitored, proving that they are really cost effective, see e.g. the links below for further information.
The picture shows the 18.000 m2 solar heating plant at Marstal Distric Heating, Ærø, Denmark. Left below you see the first 10.000 m3 test underground hot water pit storage.