Polygeneration in Portugal

1.1 Potential and legislation framework

So far, microgeneration has been largely underestimated as a potential alternative way of energy conversion. In Portugal it started to gain the deserved recognition and attention very recently. Microtrigeneration, the wide category of microgeneration, demonstrated by Polysmart subprojects 6a and 6b, is in the way for consumer autonomy. Locally produced heat, cold and power, fulfilling the individual combination of local needs can maximize synergies and strongly reduce CO2 emissions.

When compared to large-scale power production in terms of unit costs, microgeneration also performs well, with numerous comparative studies indicating its competitiveness [2]. Furthermore, since power is generated at the point of use the usual grid-based costs such as supply, transmission and distribution costs are avoided. Although requiring a different infrastructure from the one in use for the current centralised system, microgeneration starts to make economic sense in the long run if the modernisation and replacement costs associated to the existing transmission and distribution networks are considered.

The microgeneration policy in Portugal (D. L. 363 -2/Nov/2007) allows power delivery to the grid with subsided feed in tariffs for solutions until 3,68 kW based on solar power, wind power, hydro power and biomass cogeneration. Microtrigeneration should also be considered in further revisions of the present legislation.

On the other hand, buildings thermal efficiency plays a major role on local energy demands. There is specific legislation related to the subject (D. L. 78/2006; D. L. 79/2006; D. L. 80/2006), but a better conciliation with microgeneration, namely, microtrigeneration policy is desired.

It is clear that mass market microgeneration has potential to significantly supply the energy demand. Nevertheless, the rules surrounding energy trading, grid connection, planning and subsidies were developed having in mind much bigger applications, presenting serious barriers to local microcogeneration or microtrigeneration solutions.

Polysmart demo subprojects 6a and 6b are a step forward and, we hope, a significant contribution for the next regulatory framework for local energy conversion largely understood, as power, heat and cold.

So, Polysmart subproject 6b running on biodiesel is planned to be grid connected as a cogeneration unit under the present regulatory microgeneration framework. The revenue from the power delivered to the grid should be enough to face 50% of fuel costs. Subproject Polysmart 6a, running on LPG, is not under present microgeneration regulatory framework. At least, the next regulatory framework should include natural gas and LPG as privileged fuels, when substituting diesel in residential heating boilers.

Moreover, microgeneration, cogeneration or trigeneration have wider benefits as they actually act as a catalyst for cultural changes in consumer attitude, and provide evidence of the important impact that local energy production has on attitudinal and behavioural changes towards energy use. Therefore, micro generation is not only a serious form of efficient energy supply contribution, but also a solution in bridging the gap between energy efficiency and consumer behaviour and responsibility.

Considering the present experience in Portuguese PV microgeneration, grid connection is not a problem for microtrigeneration solutions. Electrical protections, such as maximum and minimum voltage, current, frequency, and island networking prevention are available on a wide range of equipments. Meanwhile, if needed, when stabilized standards, such as VDE 0126 are not applied, additional electrical protections could be included on project.

The key for microgeneration technologies to reach maximum impact lies on price to the consumer falling to competitive levels. A number of regulatory and policy changes are required to allow this to happen. Particularly, the government must set binding national targets in order to create the

necessary confidence for developers to fund mass production manufacturing capacity. There are a number of individual policy measures that would also assist the expansion of the microgeneration sector including: granting permitted development status for some approved microgenerators, detailed consideration of the export reward mechanism that allows payment for surplus electricity (when not stand alone systems) that spills on to the grid, inclusion of microgeneration within the Building Regulations and the Sustainable Buildings Code, simplifying access to ‘green energy certificates’, and the introduction of new policies for micro generators producing heat and cold. Buildings would become “micro-power stations” instead of passive consumers of energy.

Converting energy without heat dissipation at the point of use, i. e. using at least 90% of the fuel productively, is extremely efficient when compared to power stations that typically waste over 60% of the total energy released by burning fossil fuels in heat loss, and a further 10% in transmission and distribution losses.

1.2 Promising applications

From a technical-economic point of view microtrigeneration plants are more adequate for applications with permanent occupation and thermal needs.

In the last decade the number of dwellings in Portugal increased 17,2%. On the other hand, around 32% of the total number of family houses (detached and semi-detached) built in Portugal each year (22.143 including refurbishments) have four or more bedrooms [3], meaning that there is a reasonable potential for pCHCP systems in the residential sector.

The tourist accommodation sector in Portugal can also be considered to have an interesting potential for this kind of application, mainly for the hotels, apartments and resorts segments which represent around 80% of the overall capacity of the 2.031 establishments found in the country [4].

Another promising application which is growing due to population aging is the case of the nursery homes. The great energy consumption in hot water production for laundry application, constant along the year in these institutions, is important for thermal energy consumption without breaks and is also interesting to combine with solar, taking profit of the abundant resource in summer.

This kind of institution has high running costs and in most cases short budgets hence an energy efficient trigeneration solution could help solving these serious managing difficulties.

Sports halls and small office buildings may also be a good example of application.