A low cost pyrheliometer, based on a thermoelectric sensor, was developed at the Energy and Sustainability Center at the Florida State University. In addition, an inexpensive double-axis tracking device, capable of autonomous operation, enables the pyrheliometer to operate as a stand-alone system. Widely available off-the-shelf components were used and compromises in accuracy and time responsiveness were made in order to keep the cost low. The obtained data was compared with an Eppley Normal Incidence Pyrheliometer (NIP) using model ST-1 solar tracker. Steady state values of irradiance were measured with an accuracy better than $±2%$. Transient measurements are time delayed by a thermal lag of about 2 min, which leads to a high error for instantaneous measured values. However, the integrated irradiance over the course of any given day yields irradiation values with accuracy better than $±2%$, even on days when the sun and clouds quickly alternate. Based on a manufacturing cost analysis, the prototype pyrheliometer system is anticipated to cost an order of magnitude less than commercially available products if mass-produced.

## References

References
1.
Wilcox
,
S.
, and
Stoffel
,
T.
, 2008, “
Solar Resource and Meteorological Assessment Project (Solrmap). Solar and Meteorological Stations Options: Configurations and Specifications.
Technical Report, National Renewable Energy Laboratories, December.
2.
Duffie
,
J. A.
, and
Beckman
,
W. A.
, 2006,
Solar Engineering of Thermal Processes
, 3rd ed.,
Wiley
,
New York
.
3.
Iqbal
,
M.
, 1983,
,
New York
.
4.
Gnos
,
M.
, 2010, “
On the Development of a Low Cost Pyrheliometer
,” M.Sc. thesis, Florida State University, Tallahassee, FL.
5.
Spencer
,
J. W.
, 1971, “
Fourier Series Representation of the Position of the Sun
,”
Search
,
2
(
5
), p.
172
.
6.
Cooper
,
P. I.
, 1969, “
The Absorption of Radiation in Solar Stills
,”
Sol. Energy
,
12
(
3
), pp.
333
346
.
7.
WMO
, 2008,
Guide to Meteorological Instruments and Methods of Observation
. Tech. Rep. 7th ed., Part I, World Meteorological Organization, Chap. VII.
8.
Dayan
,
A.
,
Olbinsky
,
A.
, and
Mittelman
,
G.
, 2004, “
On the Design and Analysis of a Pyrheliometer Comprising a Convex Lens
,”
J. Sol. Energy Eng.
,
126
, pp.
915
920
.