The Republic of Kazakhstan has significant deposits of fossil fuels and is one of the largest energy producers among the countries of Central Asia. At the same time, The Republic of Kazakhstan is one of the richest countries of the world in terms of renewable resources, evaluated to over 1000 billion kWh/year. The application of the renewable energy sources (RES), both on a large scale and at the level of a single household, ensures the transformation of the energy system to a “green state”. However, these initiatives should be substantiated by relevant supportive information to promote transformation of the country's economy to a qualitative ecological state. The paper covers developed multi-criteria decision-making system (MCDM) and software tools for processing of spatial heterogeneous data which could be applied for evaluation of the RES potential. The developed system serves to evaluate the potential of usable RES as it allows the assessment of a territory of the country in terms of installing photovoltaic and wind generators. A feature of the proposed MCDM is the use of an analytical hierarchical process (AHP) in combination with the Bayesian approach, which allows obtaining two complementary assessments of the territory areas. The method allows a rough estimate in an event of lack of data. The verification performed based on the available data on the installed solar and wind power stations shows that the system gives a relatively small root-mean-square error within 15%.

In modern energy, various technologies for absorbing carbon dioxide from the atmosphere are being considered, including photosynthetic microalgae. An important task is to obtain maximum productivity at high concentrations of CO₂ in gas–air mixtures. In this regard, the aim of the investigation is to study the effect of light intensity on the biomass growth and biochemical composition of five different microalgae strains: Arthrospira platensis, Chlorella ellipsoidea, Chlorella vulgaris, Gloeotila pulchra, and Elliptochloris subsphaerica. To assess the viability of microalgae cells, the method of cytochemical staining with methylene blue, which enables identifying dead cells during microscopy, was used. The microalgae were cultivated at 6% CO₂ and five different intensities: 80, 120, 160, 200, and 245 μmol quanta·m⁻²·s⁻¹. The maximum growth rate among all strains was obtained for C. vulgaris (0.78 g·L⁻¹·d⁻¹) at an illumination intensity of 245 µmol quanta·m⁻²·s⁻¹. For E. subsphaerica and A. platensis, similar results (approximately 0.59 and 0.25 g·L⁻¹·d⁻¹ for each strain) were obtained at an illumination intensity of 160 and 245 µmol quanta·m⁻²·s⁻¹. A decrease in protein content with an increase in illumination was noted for C. vulgaris (from 61.0 to 46.6%) and A. platensis (from 43.8 to 33.6%), and a slight increase in lipid content was shown by A. platensis (from 17.8 to 21.4%). The possibility of increasing microalgae biomass productivity by increasing illumination has been demonstrated. This result can also be considered as showing potential for enhanced lipid microalgae production for biodiesel applications.

The influence of elevated CO₂ concentrations on the growth and viability of various microalgae strains was studied. Arthrospira platensis, Chlorella ellipsoidea, Chlorella vulgaris, Gloeotila pulchra, and Elliptochloris subsphaerica were tested. The cultivation of microalgae was carried out at constant CO₂ concentrations (0.04, 3, 6, or 9%—sequentially from lower to higher concentrations), under constant (24 h·day⁻¹) illumination with an intensity of 74.3 µmol quanta·m⁻²·s⁻¹, and a constant temperature of 23.5 ± 0.5 °C. The optical density of the microalgae biomass, pH, and the chemical composition of the culture medium were measured. Microscopy (including the cytochemical microscopic method) was conducted to monitor the state of the microalgae. The highest biomass growth rate (0.37 g·L⁻¹·day⁻¹), among all experiments, was achieved for Chlorella vulgaris at CO₂ = 3% and for Chlorella ellipsoidea at CO₂ = 6 and 9%. The lowest growth rate (0.12 g·L⁻¹·day⁻¹) was achieved for Arthrospira platensis at CO₂ = 3 and 9%. The microscopy results showed the absence or a minimum number of dead cells of the strains under selected conditions. The ability to maintain the viability of cultures up to significant concentrations of CO₂ = 9% was due to adaptation (gradual increase in CO₂ concentrations in the experiments).

Direct study of CO₂ capture efficiency during microalgae Arthrospira platensis cultivation at high CO₂ concentrations was carried out. Microalgae were grown in a 90 L photobioreactor on Zarrouk’s medium prepared with distilled water. Three 15-day experiments were carried out with different initial CO₂ concentrations: 1, 5, and 9 vol.%. During the experiments, both the change in the optical density of the microalgae suspension and the direct change in the CO₂ concentration in the chamber were measured. The maximum decrease in CO₂ concentration due to the growth of microalgae was 0.10 vol.% (CO₂)/day in the experiment with an initial CO₂ concentration of 5 vol.%. Growth rate of biomass density was 79.4, 76.3, and 48.4 (mg/L)/day at 1, 5, and 9 vol.% CO₂ concentrations, respectively. During the experiment with initial CO₂ concentrations of 1 and 5 vol.%., pH of the culture medium was increased, but pH was decreased from 9.2 to 8.8 at 9 vol.%. In general, good viability (high quality of biomass and high rate of its growth) of Arthrospira platensis was established at 1 and 5 vol. (CO₂)%, while massive death of Arthrospira platensis cells was observed in the experiment with 9 vol. (CO₂)%. Biochemical analysis of the resulting biomass revealed a decrease in the content of lipids and proteins with an increase in CO₂ concentration.

Biomass of the highly productive algae is a promising nontraditional raw material for biopower engineering, including production of energy and motor fuels from it. The paper presents an analysis of the efficiency of solar energy conversion to microalgae biofuel based both on the general theoretical approaches and on the experimental results obtained in various pilot projects. Some data on the economic efficiency of biofuel production from algae are also discussed. The possible ways to enhance the efficiency of microalgae energy use are formulated.