This communication presents a review of the literature on the test met
hods of flat-plate solar collectors under varying environmental condit
ions. The methods are classified into different groups based on their
common features. The methods are examined critically from the point of
view of their: (a) experimental procedures, (b) techniques of paramet
er identification and (c) output results. Four test procedures have be
en evaluated experimentally in detail. The results from different test
s are compared with each other and with the steady state Values based
on the ASHRAE 93-86 standard. The review reveals that test procedures
based on multi-node models may not be implemented accurately in experi
mentation. They require impractical measurements or lead to complicate
d equations for estimation of parameters. A few one-node models includ
e inconvenient test runs or confusing data reduction techniques. The r
esults of the experimental investigation indicate that Saunier's metho
d yields parameters close to those obtained on the basis of the ASHRAE
standard. However, the results are greatly affected by measurement er
rors and propagation of error in various test stages. Exell's method e
liminates the inconvenient tests of Saunier's method, but includes a l
ong chain of experiments and does not provide a good estimate of colle
ctor characteristics. Rogers' method yields a good estimate of optical
efficiency, but underpredicts the heat loss term; it also involves a
large amount of computation. The filter method leads to a good estimat
e of the heat loss term, but it overpredicts the optical efficiency. I
n addition, precise control of the flow rate and inlet temperature is
essential in the last two methods. (C) 1997 Elsevier Science Ltd.