Solar concentrator, solar receiver and thermal storage

1. A solar concentrator comprising:

a base;

a framework, the framework being hingedly joined to the base such that the framework can be rotated relative to the base; and

a plurality of mirrors arranged relative to a first axis of the framework, each mirror being fixed to the framework and each mirror being arranged to reflect light travelling parallel to the first axis towards a common focus which lies on the first axis,

the mirrors being arranged such that the first axis can be directed substantially towards the horizon of a ground plane by rotating the framework relative to the base while the base is rested on that ground plane, wherein the framework is hingedly joined to the base such that the framework can be rotated around a second axis other than the first axis, the second axis being coincident with the common focus, wherein the base is rotatable about a third axis and the third axis passes through the common focus,

wherein the plurality of mirrors form a plurality of concentric semi-circular arcs centered on the first axis, wherein each arc comprises proximate and distal edges, the proximate edge being closer to the common focus than the distal edge,

wherein the plurality of concentric arcs comprises a first semi-circular arc and a second semi-circular arc located inside the first semi-circular arc, wherein the distance between the proximate edge and the distal edge is greater in the second semi-circular arc than in the first semi-circular arc.

2. A solar concentrator comprising:

a base;

a framework, the framework being hingedly joined to the base such that the framework can be rotated relative to the base; and

a plurality of mirrors arranged relative to a first axis of the framework, such that a majority of the area of the reflective surfaces of the mirrors is located on one side of a plane which contains the first axis, each mirror being fixed to the framework and each mirror being arranged to reflect light travelling parallel to the first axis towards a common focus which lies on the first axis, wherein the framework is hingedly joined to the base such that the framework can be rotated around a second axis other than the first axis, the second axis being coincident with the common focus, wherein the base is rotatable about a third axis and the third axis passes through the common focus,

wherein the plurality of mirrors form a plurality of concentric semi-circular arcs centered on the first axis, wherein each arc comprises proximate and distal edges, the proximate edge being closer to the common focus than the distal edge,

wherein the plurality of concentric arcs comprises a first semi-circular arc and a second semi-circular arc located inside the first semi-circular arc, wherein the distance between the proximate edge and the distal edge is greater in the second semi-circular arc than in the first semi-circular arc.

3. A solar concentrator as claimed in claim 2 , wherein all of the mirrors are located on one side of a plane which contains the first axis.

4. A solar concentrator as claimed in claim 1 , wherein the plurality of mirrors comprises:

a first mirror, the first mirror being arranged a first distance from the closest part of the first axis; and

a second mirror, the second mirror being arranged a second distance from the closest part of the first axis, the second distance being greater than the first distance such that there is a gap between the first mirror and the second mirror,

the second mirror comprising a primary region and being arranged such that light travelling parallel to the first axis which is reflected by the primary region of the second mirror will pass through the gap between the first mirror and the second mirror before reaching the common focus.

5. A solar concentrator as claimed in claim 4 , wherein the plurality of mirrors further comprises a third mirror, the third mirror being arranged a third distance from the closest part of the first axis, the third distance being greater than the second distance such that there is a gap between the second mirror and the third mirror,

the third mirror comprising a primary region and being arranged such that light travelling parallel to the first axis which is reflected by the primary region of the third mirror will pass through the gap between the second mirror and the third mirror before reaching the common focus.

6. A solar concentrator as claimed in claim 1 , wherein at least one of the plurality of mirrors is curved.

7. A solar concentrator as claimed in claim 6 , wherein at least one of the mirrors describes an arc centered on the first axis.

8. A solar concentrator as claimed in claim 1 , wherein two or more of the mirrors are arranged in a first arc centered on the first axis.

9. A solar concentrator as claimed in claim 8 , wherein two or more of the mirrors are arranged in a second arc centered on the first axis.

10. A solar concentrator as described in claim 1 , wherein the framework is located on one side of a plane which contains the first axis.

11. A solar concentrator as described in claim 1 , wherein the base can rotate.

12. A solar concentrator as described in claim 1 , wherein at least one mirror comprises an aluminium plate.

13. A solar concentrator as described in claim 1 , further comprising a motor, the motor arranged to move the framework with respect to the base.

14. A solar collector which comprises a solar concentrator, the solar concentrator being according to claim 1 , the solar collector further comprising a solar receiver which is arranged to receive solar radiation from the solar concentrator such that the solar radiation heats up a fluid in the solar receiver.

15. A concentrating solar power system comprising a solar collector according to claim 14 , wherein the concentrating solar power system further comprises a thermal energy storage system, and wherein the thermal energy storage system is connected to the solar receiver such that heat from the fluid in the solar receiver can be stored in the thermal energy storage system.