Sunlight potential for microalgae cultivation in the mid-latitude region – the Baltic states
Riga Technical University, Faculty of Materials Science and Applied Chemistry, Institute of General Chemical Engineering, Pulka 3, LV-1007 Riga, Latvia
Products, e.g. food and feed from microalgae are a promising part of bioeconomy. One of the most investigated and highly demanded microalgae is Spirulina. Light is one of limiting factors for biomass cultivation by photosynthesis. Sunlight is cheap and climate friendly light source. The aim of this study was to evaluate available sunlight potential in the mid-latitude region – the Baltic states (Europe, 55–60 °N) for microalgae, e.g. Spirulina growth. The data of Climate atlas based on satellites of EUMETSAT and data from an observation station in Riga were analyzed. The latitude and climate (cloudiness) were main parameters affecting the total solar radiation received by Earth’s surface. The sunlight potential in the Baltic states was higher than in most of Europe in similar latitude. Multi-year mean daylight intensity in the Baltic states was slightly less than in Southern France or Bulgaria, (26 klux and 30 klux, respectively, in summer) where Spirulina is commercially produced. Hourly solar radiation varied a lot in the Baltic states – from 880 W m-2 to 200 W m-2, sunny and overcasted noon of summer day, respectively; average value (8 a.m.–4p.m.) was 450 W m-2. Summer days are longer than 12 h, reaching 18 h in midsummer. The sunlight potential is suitable for microalgae, e.g. Spirulina cultivation in this period. From November till February days are shorter than 10 h and solar radiation is less than 300 W m-2 even in noon of sunny days.