SOLAR-WIND HYBRID INSTALLATION

Introduction.

In the following article, we are going to expose a type of renewable energy installation that can be, on many occasions, the optimal domestic solution. Specifically, we will see the solar-wind hybrid installation.

This installation combines the energy from the sun to obtain electrical energy through photovoltaic panels, and the energy from the wind to obtain electricity through a wind turbine.

What is intended to achieve with this type of installation is a more homogeneous energy supply throughout the year. Compensating for the lesser amount of solar energy obtained during the winter months, with the contribution of wind energy.

Before starting, we must clarify that we are going to refer exclusively to situations that occur in countries of the tropical fringe, where the seasons of the year are different. In areas of the equatorial belt should be considered other situations of climatic stability, hours of sunlight, etc.

Consumption estimation.

The first piece of information that we will have to calculate, will be the demand for electrical energy. Paying special attention to its distribution month by month.

The electricity consumption due to lighting is certainly higher in winter, because we have fewer hours of light. However, considering the current use of energy saving lamps, this factor will have little influence today. Most of the electricity consumption is due to house appliances.

In areas with cold winter, the heating is not installed electrically, because the obtaining of heat by the Joule effect, has a great energy waste and the regulations prohibit it. In these cases, the heating is installed by means of heat-transferring water pipes and radiators. Therefore, for our calculation of electricity demand, what we should consider as consumption, would be mainly the circulation pumps.

In milder winter areas, it may be usual to install Split-type equipment that works in "heat pump" mode for heating (Joule effect).

The most significant annual consumption will always be the air conditioning for refrigeration. For the calculation of electricity demand, its temporary nature must be considered, exclusively during the summer months.

Example of calculating consumption of a single-family home with air conditioning in kWh:

• Lighting                      11W                30u   5h/day           1.65kWh/day
• Refrigerator              300W              1u     2h/day           0.6kWh/day
• Cooktop                   4500W            1u     0.2h/day*      0.9kWh/day
• Extractor                   100W              1u     0.2h/day*      0.02kWh/day
• Oven                         1500W            1u     0.2h/day*      0.3kWh/day
• Microwave               800W              1u     0.1h/day*      0.08kWh/day
• Washing machine   1500W            1u     1h/day*         1,5kWh/day
• Dishwasher               1500W            1u     1h/day*         1,5kWh/day
• TV                               200W              1u     4h/day*         0.8kWh/day
• Computer                 500W              1u     2h/day*         1,0kWh/day
• Several outlets         1000W            1u     1h/day*         1,0kWh/day
• Air Conditioning      2500W            1u     1h/day**        2,5kWh/day

TOTAL:                                                                                   11.85kWh/day

(* weekly average; ** weekly average only in summer)

Monthly distribution of electricity consumption and production. Various examples.

Next, for your better understanding, we will analyze several typical cases. Solar energy production will be higher during the summer months, in all cases. The production of wind energy will be of a different type for each case:

• Case 1. High wind production during the winter months and low during the summer months.

This case is what we would call the ideal case for installing a hybrid type installation. The lower contribution of solar production during the summer months will be offset by wind energy production during the rest of the year.

In the ideal case, electricity consumption could be covered month by month, by the sum of solar electricity production with wind electricity production, without there being an excessive energy surplus in any month.

• Case 2. Constant annual wind energy production.

In this case, it could be that the solar energy installation is not needed, because only with the wind installation, we would cover our energy needs throughout the year.

Other aspects such as the profitability of each type of installation should be analyzed. Or if there was some other problem, such as an environmental one.

You would only be interested in an additional solar installation, in case you have extra consumptions in summer. Thus, if we are going to install a wind installation, the electrical power of this solar installation must be exclusively to cover these extra consumptions in these summer months.

• Case 3. High wind production during the summer months and low during the winter months.

In this case, the hybrid installation will normally not be recommended. It will be classified as not economically viable.

You can choose either solar or wind installation, whichever is the most profitable in a unique way. But in principle, the hybrid installation will not be the most suitable.

In the winter months, we will need an auxiliary external contribution to cover our energy demand, because in this case, neither with a renewable wind or solar installation, it would be covered.

• Case 4. Wind production variable annually and unpredictable according to statistical data.

The range of uncertainty should be analyzed in case there is any possibility, but normally the wind installation would not be viable.

A solar-type installation could normally be installed, if feasible.

Optimization of the equipment for our facility.

The next step will be the sizing of our hybrid installation, a combination of solar and wind energy installation. The production of electrical energy must be adjusted as much as possible to the time distribution month by month of consumption. Next, we explain the importance of this fact:

• In the event that, at any given time, we produce more electrical energy than we consume, we will be having an excess production, not directly used. This excess will be stored in the batteries.
• If, on the contrary, at another time, we produce less electrical energy than we need, it may be obtained from the energy previously stored in the batteries.

Thus, the better the time adjustment from production to consumption, the smaller and cheaper our batteries can be.

If this setting is bad, the installation will not be optimized and will be more expensive. And since these batteries are one of the most expensive components of any electrical installation, you will have to pay more for the acquisition of equipment that would not really have been necessary.

Conclusions. Investment optimization.

The sizing of the solar and wind installations of our hybrid installation will be done taking into account the potential of our situation, depending on our location. We will analyze if we are in any of the cases presented in the previous graphs, or if at least we have a similar trend.

Actual consumption will be properly estimated month by month. Observing if there are possible situations of simultaneity, so as not to design an oversized installation.

With this, we will be able to know in what percentage approximately of the solar-wind mix each one will participate.

Finally, the availability of existing equipment on the market will be studied. Well, with our specific needs, we will have to select the components of our installation from the sizes provided by the manufacturers.

Other factors will be taken into account, such as the initial cost of the equipment, the amortization in a given period of time based on the price of electricity, etc.

In addition to all these economic considerations, it should be studied whether there is any possible type of negative environmental impact.

With all these considerations, we will be in a position to decide exactly the installation we need, absolutely adjusted and optimized for our specific case.

Written by: Carlos Gerardo Béjar Ramírez_ 09.10.2020

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