A power plant comprising: a solar receiver configured to heat solid particles; a standpipe extending downward from the solar receiver to receive solid particles from the solar receiver, the standpipe having a height sufficient to support a column of heated solid particles of height H; a pressurized heat exchanger configured to operate at an elevated pressure higher than atmospheric pressure to heat working fluid flowing through the pressurized heat exchanger by heat transfer from heated solid particles flowing out of the bottom of the standpipe wherein the working fluid is a gaseous medium; and a flow path for solid particles from the bottom of the standpipe into the pressurized heat exchanger that is configured to be sealed by a pressure P produced at the bottom of the standpipe by a column of heated solid particles of the height H, wherein the flow path includes a non-mechanical valve configured to regulate flow of the solid particles from the bottom of the standpipe into the heat exchanger by controlling a flow of working fluid in the non-mechanical valve; and wherein the solar receiver comprises: an annular volume through which granular solid particles flow downward; and light-channeling tubes having apertures at the outer surface of the annular volume to receive light from a heliostat field and extending into the annular volume so that the downward flowing granular solid particles pass over the light-channeling tubes to absorb solar thermal energy. a solar receiver configured to heat solid particles; a standpipe extending downward from the solar receiver to receive solid particles from the solar receiver, the standpipe having a height sufficient to support a column of heated solid particles of height H; a pressurized heat exchanger configured to operate at an elevated pressure higher than atmospheric pressure to heat working fluid flowing through the pressurized heat exchanger by heat transfer from heated solid particles flowing out of the bottom of the standpipe wherein the working fluid is a gaseous medium; and a flow path for solid particles from the bottom of the standpipe into the pressurized heat exchanger that is configured to be sealed by a pressure P produced at the bottom of the standpipe by a column of heated solid particles of the height H, wherein the flow path includes a non-mechanical valve configured to regulate flow of the solid particles from the bottom of the standpipe into the heat exchanger by controlling a flow of working fluid in the non-mechanical valve; and wherein the solar receiver comprises: an annular volume through which granular solid particles flow downward; and light-channeling tubes having apertures at the outer surface of the annular volume to receive light from a heliostat field and extending into the annular volume so that the downward flowing granular solid particles pass over the light-channeling tubes to absorb solar thermal energy. an annular volume through which granular solid particles flow downward; and light-channeling tubes having apertures at the outer surface of the annular volume to receive light from a heliostat field and extending into the annular volume so that the downward flowing granular solid particles pass over the light-channeling tubes to absorb solar thermal energy.