Units and Equivalences - Greenhouse Technology and Management - page 301

Pressure

1 kilopascal (kPa) = 1000 Pa
1 pascal (Pa)

= 1 newton per square metre (N m −2 )

1 milibar (mb) = 100 Pa

1 centibar (cb) = 1000 Pa = 1 kilopascal (kPa)

1 bar (b) = 0.987 atmospheres = 0.1 megapascales (MPa)

Energy and Power

1 joule (J) = 0.239 calories (cal)
1 calorie (cal) = 4.18 joules (J)
1 watt (W) = 1 joule per second (J s −1 )
1 kilowatt-hour (kWh) = 3600 kilojoules (kJ)
1 kilowatt-hour (kWh) = 3.6 megajoules(MJ)
1 kilowatt-hour (kWh) = 860 kilocalories (kcal)

Radiation

Solar constant:
1353 W m −2 = 4871 kJ m −2 h −1 =
1940 cal cm −2 min −1 = 1940 Ly min −1
Radiation intensity (irradiance):
1 W m −2 = 1.434 10 −3 cal cm −2 min −1

1 cal cm −2 min −1 = 697.3 W m −2

Cumulated radiation:
1 langley (Ly) = 1 cal cm −2 = 41.84 kJ m −2
1 kilolangley (kLy) = 1000 Ly
1 kWh m −2 = 3.6 MJ m −2

1 kWh m −2 = 860 kcal m −2 = 86 Ly

Water Lamina

1 litre per square metre (l m −2 ) = 1 mm = 10 m 3 ha −1

Prefixes

n (nano) = 10 −9
m (micro) = 10 −6
m (milli) = 10 −3
k (kilo) = 10 3
M (mega) = 10 6
G (giga) = 10 9