ARTICLE Efficient Car Parks for the 21st century

INTRODUCTION

One of the challenges facing society in the 21st century is energy-saving. The increasingly unstable situation in the oil production industry and with other energy sources, coupled with demands for environmental improvement, makes a sustained and unstoppable increase in the price of electricity likely. All sectors that consume (domestic, service, industrial) will be affected. The world of garages and car parks, as an electricity consumer, is related to this steady increase in operational costs caused by rising electricity bills. This article aims to analyse the origin of electrical consumption in garages and car parks and propose solutions that help reduce it by optimising their installations and equipment.

DISTRIBUTION OF ELECTRICAL CONSUMPTION IN GARAGES AND CAR PARKS

Existen diferentes tipos de garajes y aparcamiento: exterior, edificio semiabierto y subterráneo. Nuestro estudio se centra en los semiabiertos y subterráneos. En ellos se consume energía eléctrica para el abastecimiento de los sistemas de iluminación, extracción de humos, elevación, detección de incendios y gases, cajeros de pago, control de accesos, tal como se muestra en la figura 1.

Figure 1.- Electrical consumption in a car park

The quantitative distribution of electrical energy consumption (KWh) in a garage or car park depends on its type of construction, location, conditions of use, opening hours... An average estimate is that shown in figure 2.

Figure 2.- Average distribution of electrical consumption in a garage or car park

Consumption of electricity for lighting (equivalent to 42% of total consumption) is almost always from fluorescent light. There are regulations that establish minimum levels of lighting in buildings, including garages or car parks.

Consumption of electricity for extraction (equivalent to 38% of total consumption) comes from the need for air exchange and extraction in the enclosed area, which is contaminated primarily by combustion gases from vehicles (carbon monoxide CO, nitrogen oxide derivatives NOx etc.). There are mandatory regulations that require the installation of air exchange systems. There are also regulations that require CO carbon monoxide detection systems to be installed, which activate an alarm if dangerous levels are reached.

To better understand the origin of electricity consumption and its potential savings, different types of semi-open and underground car parks have been categorised:

Private: Parking spaces are owned, leased or belong to season ticket holders. These are small garages, normally belonging to residents' associations. Lighting is controlled by timers (time delay) or manually. Extraction is controlled by time switches (time on/off) or manually
Public: Spaces are occupied on a rotational basis (sometimes combined with season ticket holders). These are medium and large garages in city centres, shopping centres and airports. These car parks tend to remain permanently lit during opening hours, with no automatic control (or very often no manual control either). Extraction is controlled manually by time switches and sometimes by connecting the extractors to an on-off alarm mechanism (relay) in the CO carbon monoxide switchboard.

As can be seen, there is a lot of lighting and fume extraction savings potential in a garage or car park.

Note: We have not analysed the consumption of other elements that regularly consume electrical energy in a garage (elevation, payment systems, access control, fire detection, etc.) because individually they do not offer major savings potential.

SYSTEMS FOR OPTIMISING ELECTRICAL CONSUMPTION IN A GARAGE OR CAR PARK

Systems that help achieve a significant saving in electrical consumption are:

a)LED lighting instead of fluorescent lights: The replacement of traditional fluorescent lights with LED systems is a rising trend. Indeed, LED light output is three times higher than fluorescent, or rather, for equivalent lux, LED electrical consumption is three times less than fluorescent. Moreover, the useful life of LED (approx. 60,000 hours) is far longer than fluorescent (approx. 3,500 hours), so when considering maintenance costs the advantages weigh heavily in favour of LED. But that is not all, LED light intensity control is very easy and economical because a direct current voltage of less than 50 volts is being controlled. The same control in fluorescent lights is technically possible but very costly, because we would have to control 230 alternating current volts and these lights do not tolerate control very well (switching on fatigue and gas maintenance which reduces their life). We therefore propose, simply and economically, to detect the presence (or absence) of vehicles or persons within the enclosed area (installation of motion sensors) and reducing (or even turning off) the lighting in this area (figure 3). That is why the potential saving in LED lighting compared to fluorescent is more than 66% than mentioned previously. This will depend on the volume of pedestrian and vehicle traffic, which varies in each garage or car park. Even so, we can establish that the average saving in lighting in a car park with 50% traffic (half the time the lights are switched on without people or vehicles present) would be 75%. In other words, in an average garage, where 42 KWh out of 100 KWh would be consumed with fluorescent lights, we could reduce this to 11 KWh with controlled LED lighting, i.e the potential saving would be 75%.

Figure 3.- LED lighting system with motion detection control

Figure 4.- View of an underground car park with controlled LED lighting.

LED lighting requires higher investment but the payback period is reasonable because, on average, after the third year the saving starts to pay for the investment.

Figure 5.- Return on investment in LED lighting versus fluorescent.

b) CO ramp ventilation instead of manual or time-controlled: The installation of a CO carbon monoxide detection system (mandatory in Spain and other countries) is an opportunity for optimum control of electrical energy consumed in ventilation. The CO detection system must be programmed to collect the average CO value in its area of influence and it must have an analogue control output proportional to the CO measured. This signal will be used as an input variable in an adjustable speed drive which controls the speed of the fume extraction fan motor (technically known as a variable frequency drive or inverter). When the average CO value approaches the assigned set-point (50 ppm of CO), the motor will run very slowly, but this would increase if the extraction level was not sufficient (figure 6). An additional benefit of the system is the soft starter which produces additional power savings and its own fume extraction system has a longer life. This system guarantees minimum consumption in fume extraction. An additional advantage is the greatly reduced extractor noise because it will almost always run at low speed. In summary, where in our average garage 38 KWh out of every 100 KWh would be consumed in fume extraction with conventional systems (manual or time-controlled), we could reduce this amount to 23 KWh with CO ramp controlled ventilation, achieving savings of up to 40%.

Figure 6.- Ramp ventilation system according to level of CO

c) Vehicle guidance system combined with previous improvements: Vehicle guidance systems are traditionally installed in a garage or car park to make life easier for the user (helping them to locate free spaces more quickly), to obtain greater profitability for the owner (increase in percentage occupancy) and to provide a modern image of the car park. Although it might appear obvious, a car park's vehicle guidance system results in an electrical energy saving in itself. If vehicles take less time to park it means they will pollute less and extraction will be reduced (if CO ramp controlled). There will also be a saving in lighting (if the system is LED and controlled by motion detection):

Figure 7.- Guidance system combined with LED lighting and CO ramp extraction control

Figure 8.- Efficient Parking System switchboard

COMPARISON OF ELECTRICAL CONSUMPTION WITH AND WITHOUT OPTIMISATION IMPROVEMENTS

We have seen that the estimated potential saving achieved with the proposed measures is as follows:

Lighting: LED lighting, with motion control: 75% saving
Fume extraction: CO ramp fume extraction control 40% saving
Total car park consumption saving 47% saving

The quantitative distribution of electrical energy consumption (KWh) in our garage or car park is now different with the application of energy-saving measures. An average estimate is shown in figure 9.

Figure 9. Distribution of electrical consumption in an optimised car park

When comparing the level of consumption with and without improvements that save electrical energy (KWh) we can see that, from an initial consumption of 100 KWh, we would drop down to values of 53 KWh, resulting therefore in an estimated potential saving, in total electricity consumption in the car park of 47%. As explained, the saving would depend in each case on the conditions of use, type of construction and types of control for both lighting and fume extraction.

Fig 11.- Electricity consumption (KWh) before and after savings measures

USEFULNESS OF MONITORING ELECTRICAL PARAMETERS:

Monitoring parameters is key to the effectiveness of any energy savings measure. Measurement equipment and good Scada software must be installed to check continuous good electricity consumption performance and detect possible anomalies or changes that might lead to increased consumption. An example is shown in figure 12. Through Scada software connected to the system, not only will we be able to check that the ratio of electrical consumption to car park occupancy is correct, but we will also be able to accurately check the consumption distribution (lighting, fume extraction, etc.), consumption record and generation of useful alarms for the operator (events). For maintenance purposes, it is equally important to install electrical parameter metering equipment to prevent future problems in both the amount of the electricity bill (maximum power, reactive power penalty, flat rate etc.) as well as any equipment failures that might jeopardise the operation of the car park itself (faulty extraction motors, UPS offline, payment system out of order etc.). If it is quality software, the technology allows us to also manage and control different car parks from a remote location, or even from a mobile phone (BlackBerry or similar). It is advisable to install metering equipment not only in the service connection or main line but in different branch circuits of the electrical installation (lighting, fume extraction, elevation, barrier and payment systems, fire and gas detection etc.). This could also be done on different levels or in different zones for a large car park.

Figure 12.- Example of monitoring of general and specific consumption in a car park

POSSIBILITY OF CHARGING ELECTRIC VEHICLES WITHOUT INCREASING POWER:

The Electric Vehicle (EV) is a media reality that does not reflect the small number of vehicles currently in circulation on the roads today. This situation will change when car dealers' showrooms (cars, motorcycles, bicycles, industrial vehicles, buses, etc.) start to exhibit these vehicles. Such a change will occur within a few months and, in particular, over the next few years, since the major car manufacturers are developing their own EVs. Garages and car parks are ideal for charging EVs because, apart from the driver's own home or office, these are the places where they spend most time stationary. But the electrical installation of the existing garage or car park does not have spare power for charging EVs. In most cases, it will not be possible to increase the amount of power supplied by the electricity company. So it will be very important to reduce the amount of power demanded, to use this to charge EVs. As already seen, converting a conventional car park into an efficient car park will reduce the amount of power required for lighting and fume extraction from 100 to 53, allowing us to charge the EV without having to increase power, which in many cases would not have been possible for technical reasons.

Figure 13.- Charging an electric vehicle in an underground car park with parking guidance and LED lighting.

CONCLUSIONS:

The price of electricity is one of the fixed costs of the car park and garage sector which has most increased over the past ten years, and which, undoubtedly, will continue to rise over the next five years or so. We estimate that, on average, 80% of electrical consumption in an underground or semi-open car park is for lighting (42%) and fume extraction (38%). We will achieve consumption reductions of around 50% through the combined installation of the following systems:

LED lighting, with motion control.
Fume extraction, with CO ramp control.
Vehicle guidance, from space to space.
Monitoring and management of electrical parameters using Scada software.

The power reduction obtained with the systems described will help charge any Electric Vehicles in the car park without having to increase the service connection.

Efficient car parks are not optional, they are a necessity in the 21st century. Saving electricity is just one of many benefits of their unstoppable metamorphosis. Customer loyalty, greater respect for the environment and a more diverse service (with car parks operating as more than just a storage facility for cars) provide a more innovative vision than ever before of this activity.

Figure 14.- Summary of innovative technologies in the car park of the 21st century