A heat receiver tube for absorbing solar energy and for transferring absorbed solar energy to a heat transfer fluid which can be located inside of at least one core tube of the heat receiver tube is provided. The core tube includes a core tube surface with at least one solar energy absorptive coating for absorbing solar radiation. The core tube is enveloped by at least one enveloping tube. The enveloping tube includes at least one enveloping tube wall which is at least partly transparent for the solar radiation. The enveloping tube wall includes at least one inner enveloping tube surface. The core tube and the enveloping tube are coaxially arranged to each other such that an inner heat receiver tube space is formed which is bordered by the core tube surface (and the inner enveloping tube surface.

A heat receiver tube for absorbing solar energy and for transferring absorbed solar energy to a heat transfer fluid which can be located inside of at least one core tube of the heat receiver tube is provided. The core tube includes a core tube surface with at least one solar energy absorptive coating for absorbing solar radiation. The core tube is enveloped by at least one enveloping tube. The enveloping tube includes at least one enveloping tube wall which is at least partly transparent for the solar radiation. The enveloping tube wall includes at least one inner enveloping tube surface. The core tube and the enveloping tube are coaxially arranged to each other such that an inner heat receiver tube space is formed which is bordered by the core tube surface (and the inner enveloping tube surface.

A foldable parabolic solar collector includes a first panel having a semi-parabolic reflective inner surface, a central tube to which the first panel is fixed, and a second panel having a semi-parabolic reflective inner surface. The second panel is pivotably mounted to the central tube with the reflective inner surface of the second panel facing the reflective inner surface of the first panel. A receiver tube carries a heat transfer fluid. A tracking motor rotates the central tube. A torque sensor lies in between the tracking motor and the central tube and is configured to measure torque between the tracking motor and the central tube. A servomotor pivots the second panel about the central tube between an open position and a closed position when it is determined by a controller that the torque between the tracking motor and the central tube exceeds a predetermined torque threshold.

A system and method for cleaning surfaces is disclosed. The system includes an elongated blade configured to remove at least one of dirt, dust, debris and film from a smooth surface. A drive system is provided for causing the blade to contact the entire smooth surface, thereby removing at least a portion of at least one of dirt, dust, debris, and film. A cleaning device automatically cleans the blade before and after the blade is cleaning the smooth surface. In one example, system is part of a heliostat system for use in a solar collection field as part of a concentrated solar power (CSP) plant.

A solar collector housing that is opened and closed without tools includes structure for accommodating temperature-related expansion and contraction of a polymer absorber housed within the collector. The housing includes a transparent cover, a frame for holding the transparent cover, and a base. The cover, frame and base collectively define a hollow interior within which the polymer absorber is positioned. A plurality of latches is secured to an exterior of the frame. The frame and base are pivotally connected to one another when the latches are open so that the collector housing can be opened. The housing cannot be opened when the latches are closed. A pair of variable gate closure components are positioned in slots formed in a second end of the collector and enable the polymer absorber to expand and contract without placing stress on the absorber tubes.

A solar collector housing that is opened and closed without tools includes structure for accommodating temperature-related expansion and contraction of a polymer absorber housed within the collector. The housing includes a transparent cover, a frame for holding the transparent cover, and a base. The cover, frame and base collectively define a hollow interior within which the polymer absorber is positioned. A plurality of latches is secured to an exterior of the frame. The frame and base are pivotally connected to one another when the latches are open so that the collector housing can be opened. The housing cannot be opened when the latches are closed. A pair of variable gate closure components are positioned in slots formed in a second end of the collector and enable the polymer absorber to expand and contract without placing stress on the absorber tubes.

A heat receiver tube for absorbing solar energy and for transferring absorbed solar energy to a heat transfer fluid may include: a core tube with a solar energy absorptive coating for absorbing solar radiation, the heat transfer fluid at least partially inside the core tube; and an enveloping tube surrounding the core tube, the enveloping tube including an inner enveloping tube surface. The core tube and the enveloping tube are coaxially arranged forming an inner heat receiver tube space. There is an inert gas in the inner heat receiver tube space. The tube may further include a dimension adapting device having a flexible adapting device wall compensating for thermally induced changes in a dimension of the tube. The enveloping tube and the dimension adapting device are joined together by a skirt having an inlet port for the inert gas. The inlet port is sealed with a metal.

A solar collector may include a frame for supporting a plurality of photovoltaic (PV) panels. The frame may be adapted to removably attach to a base. The solar collector may include a first panel assembly, including at least one of the plurality of PV panels, pivotally attached to the frame about a first axis. The solar collector may also include a second panel assembly, including at least one of the plurality of PV panels, pivotally attached to the first panel assembly. The second panel assembly may collectively move with the first panel assembly about the first axis and to pivot relative to the frame, and to pivot about a second axis that is substantially parallel to and radially offset from the first axis, to move between a deployed position and a retracted position.

Photovoltaic tracking systems with a ratcheting stow mechanism are provided. In particular, tracking systems allow for controlled movement of photovoltaic panels adapted for solar tracking to a stowed configuration without requiring electrical power. Such mounting systems can include a partially toothed ring gear with a pair of pawls pivotally mounted adjacent the ring gear with a pair of solenoids that when de-energized, move the pawls into engagement with the ring gear such that ratcheting movement of the pair of pawls along the ring gear in response to back-and-forth oscillating movement of the panel incrementally moves the panels into a stowed configuration without requiring use of electrical power.

Methods of arranging and operating a molten salt solar thermal energy system are disclosed. Molten salt flows from a set of cold storage tanks to solar receivers which heat the molten salt to a maximum temperature of about 850 F. The heated molten salt is sent to a set of hot storage tanks. The heated molten salt is then pumped to a steam generation system to produce steam for process and/or power generation. Lower salt temperatures are useful in processes that use lower steam temperatures, such as thermal desalination. Lower salt temperatures and low chloride molten salt reduce the corrosion potential, permitting the use of lower cost alloys for the solar receivers, hot storage tanks, salt pumps, piping and instrumentation and steam generation system. Multiple sets of modular, shop assembled storage tanks are also used to reduce the amount of salt piping, simplify draining, and reduce field assembly and plant cost.