The HELIOtube is a radical departure from conventional CSP technology, as it is based around tubes of inflatable plastic film.
Instead of directly turning sunlight into electricity, as solar photovoltaic cells do, concentrated solar power systems, which focus a large area of sunlight onto a small area, can be an efficient means for harnessing some of the thermal energy for use either directly, as steam, or indirectly, by converting it into electricity. There are many types of concentrated solar power (CSP) technologies, with perhaps the most recognizable form being that of the ‘solar power tower‘ that features hundreds of heliostats (dual-axis tracking reflectors) that direct sunlight onto a thermal receiver on top of the tower, and which gets the brunt of the complaints from solar naysayers for the toll on birds. However, another CSP technology, parabolic trough systems, focuses the sunlight on a receiver much closer than a solar tower, heating up a tube within the trough to harvest the thermal energy, which avoids the bird-killing issue.
A new approach to CSP has some similarities to parabolic trough systems, in that it also concentrates sunlight onto a central thermal receiver, but the new technology from Heliovis aims to do away with the high costs of conventional trough systems, while also adding a lot of flexibility, in that its CSP systems are designed to be transportable, not permanent. The HELIOtube technology, which is based on a system of plastic films instead of rigid parabolic mirrors, is said to cost about 55% less than conventional trough systems, and to represent a CO2 emissions savings of 40%, because its lightweight materials are much less resource-intensive to manufacture and can be recycled at their end of life.
The HELIOtube CSP system is an enclosed cylinder that takes shape through inflation, and which uses a transparent film on the top to allow for the sunlight to enter it, where a “mirror film” reflects it onto a thermal receiver to bring the fluid within to temperatures of 400 to 600° C. Two airtight chambers are created within the tube and the mirror film is shaped by a slight pressure differential between the two, and the entire cylinder is supported by aluminum trusses and steel framing. The heat transfer fluid running through the receiver can then supply heat directly or be used to generate steam, which then produce electricity by spinning turbines. A few other applications for the technology are suggested by Heliovis, such as solar cooling, water desalination, and enhanced oil recovery efforts, and one of the most compelling features, its transportability, could make systems like this much faster to deploy, and with a much smaller carbon footprint.
“These collectors are manufactured from roll-to-roll and in large quantities from commercially available, recyclable plastic films each extensively proven in various industrial applications and in desert environments. Every rolled-up and unbreakable collector can be shipped in a standard 40 foot container also to remote areas. On site, the solar collector is inflated by air instead of assembling and aligning thousands of glass mirrors which is very time consuming, costly, and open to mistakes. Through inflation the collector becomes self-supporting and aerodynamic.” – Heliovis
According to Heliovis, a HELIOtube system can be rolled up and transported in a standard shipping container, and then inflated once on the site, which represents a significant advantage over other CSP trough systems in logistics costs alone. In June, the company commissioned “the first industrial application of this technology” using commercially available plastic films at an pilot project installation in Spain, where the 1 megawatt, 200-meter long, 9-meter wide, system features a “world-record homogenous mirror of about 1,600 m2 (8 m width and 200 m length).” The system, which also has a thermal storage component that maintains heat generation after dark, provides process heat for mushroom production and is expected to save the client “tens of thousands of litres of diesel fuel.”
“Conventional CSP technologies use large quantities of steel and glass. As a result strong heavy foundations are needed. This excessive use of resources comes at a cost in production, transport as well as in future waste management. The HELIOtube is made of plastic films by a patented design creating a significant reduction of weight (e.g. 90% reduction compared to parabolic troughs), which results in lower transportation costs.” – Heliovis
Learn more about the HELIOtube CSP system at the Heliovis website.