#10 Energy: a major challenge for sustainable building in the Antilles
Energy consumption is growing rapidly in the Caribbean, both as a result of population growth and the very strong economic growth of the last twenty years. Committed to a sustainable development approach, France must implement strategies to limit energy consumption in these overseas departments, which are characterized by their tropical climate and their tendency to use expensive and polluting air conditioning systems. Pricillia Privat, head of the H3C-CARAïBES design office in Guadeloupe and Loic Nohilé, project manager in the Martinique agency, have agreed to discuss energy issues in the Antilles.
What is the place of renewable energies in the energy mix of Guadeloupe and Martinique?
Deprived of local fossil energy resources, renewable energies already represent a significant part of the energy balance of these territories. Nevertheless, history, as much as geography, has made Overseas France highly dependent on imports of fossil energy resources. The strengthening of its energy autonomy is therefore a primary objective and this must necessarily involve renewable energy.
In the case of Martinique, about 75% of the energy is now produced by fuel oil, via a thermal power plant that supplies the entire island. The rest of the energy mix is divided between photovoltaic (7%) - thanks in particular to 3 large solar power plants -, wind power (17%), and biomass (bagasse combustion).
Guadeloupe's mix is similar to that of Martinique, with about 19% of renewable energy: photovoltaic (6%), geothermal (5%), bagasse (3%), wind (3%) and hydro (2%).
Which renewable energies should be prioritized?
The use of solar panels in the French Antilles is a natural choice given the amount of sunshine. The climate of the Caribbean islands being of a tropical type, the sun is present almost all year round. Concerning wind power, Guadeloupe and Martinique also meet the necessary conditions for its proper functioning: the wind is particularly strong, especially during the period of the Trade Winds (from November to May).
The first grid-connected wind farm, which was inaugurated in February in Grand-Rivière, will supply 10,000 Martinique households. Two other very large parks are currently under construction. The ambition is to make the overseas territories totally autonomous in terms of energy thanks to renewable energies by 2030. Less well known than solar and wind energy, geothermal energy is by far the most powerful renewable energy of all but still remains largely under-exploited.
Does this 2030 target for energy autonomy seem reasonable to you?
Beyond energy production, it is essential to act on the building level, so that this sector is less demanding in terms of energy consumption. One of our main concerns is the rapid development of air conditioning. In the Antilles, the most popular household electrical appliances remain this one, with a multiplication of commercial offers in recent years that have accompanied massive household equipment.
In rental for example, the presence of air conditioning is a plus for the rent price. It is therefore difficult to define the places where it is really necessary, speculative uses, or even motivated by a desire to demonstrate an image of success.
Building dwellings without air conditioning today is necessary, but not sufficient. Experience shows that many households are equipped afterwards. Campaigns to acquire more efficient equipment have been set up to meet this challenge. We must now succeed in raising people's awareness of their practice. Make it clear that the fact that it is cool in a home is no longer a criterion for giving a modern self-image.
What is the alternative to air conditioning?
First, take into account local construction constraints. In metropolitan France, to save energy, we generally have to limit the supply of cold air from outside during the winter. In the Antilles, where the climate is tropical, we have the opposite constraint all year round: in order to reduce the need for air conditioning, we use airflow, allowing us to have a high renewal and air speed in buildings, which increases the feeling of comfort. The ideal way to optimize this feeling is to design a through housing, offering an opening to the outside on at least two facades of different orientations. With relatively constant trade winds, this is East/West for the Antilles. This configuration allows for better ventilation within the dwelling and offers the possibility of surventilage during the night in summer. In addition, the fan is preferred to air conditioning systems, which are much more energy-consuming.
The most important thermal contributions coming from radiate solar energy are the use of solar masks on walls and roofs. Insulation is not very important in this type of climate, while solar masks to avoid direct contact with the sun are much more effective. On the other hand, we are also trying to favor natural lighting over artificial lighting, of course. The problem is that there is an antagonism between the reduction of electricity and natural lighting and since the heat increases with the last one: it is therefore a balance that the designer must seek to achieve. It is also possible to influence the color of the buildings since the absorption of the building varies according to it. The solar impact is much less important for white, whose wavelengths reflect the light rays. These bioclimatic approaches are increasingly being adopted by social landlords, who generally do not use air conditioning in their homes, as well as in school buildings.
You talk about bioclimatic approaches, are the computer calculation tools you have at your disposal adapted to the Antilles?
Yes and no, of course we use traditional tools, but in terms of flow dynamics, we are obliged to review certain factors. Development teams are based mainly in temperate climate zones, as are most users. We also lack data because there are few weather stations on the islands.
However, this is a matter of detail. Before talking about technology, it is necessary to take into account the local reality. We often have only one project per year that can afford this type of service. For the rest, we are more confident in advanced advice, which requires a very good knowledge of local realities. The presence of design offices like ours in the Antilles and therefore fundamental to massify energy savings.
Returning to energy, what is the place of self-consumption in the Antilles?
The main obstacle to this is the discontinuous nature of production, both in terms of collective production and self-consumption at the household level. Here, the question of storage is far from being resolved. Nowadays, the current self-consumption is exclusively based on solar energy. Whether in Martinique or Guadeloupe, we are already talking about a photovoltaic production that is almost insignificant on a mix scale and the private sector is now a tiny part of it. In other words, paradoxically, self-consumption is almost non-existent despite the significant potential in solar energy. Unfortunately, there is no risk of a reversal of the trend, as buyback costs are constantly decreasing.